Patent Publication Number: US-2021163976-A1

Title: Genetically altered plants expressing heterologous receptors that recognize lipo-chitooligosaccharides

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 62/718,186, filed Aug. 13, 2018, which is hereby incorporated by reference in its entirety. 
    
    
     SUBMISSION OF SEQUENCE LISTING AS ASCII TEXT FILE 
     The content of the following submission on ASCII text file is incorporated herein by reference in its entirety: a computer readable form (CRF) of the Sequence Listing (file name: 794542000340SEQLIST.txt, date recorded: Aug. 12, 2019, size: 253 KB). 
     TECHNICAL FIELD 
     The present disclosure relates to genetically altered plants. In particular, the present disclosure relates to genetically altered plants containing a nucleic acid sequence encoding a heterologous receptor polypeptide. The plants are able to recognize lipo-chitooligosaccharides (LCOs) through the heterologous receptor polypeptide. 
     BACKGROUND 
     Plants are exposed to a wide variety of microbes in their environment, both benign and pathogenic. To protect against the pathogenic microbes, plants have the ability to recognize specific molecular signals of the microbes through an array of receptors and, depending upon the pattern of the signals, can initiate an appropriate immune response. The molecular signals are derived from secreted materials, cell-wall components, and even cytosolic proteins of the microbes. Chitooligosaccharides (COs) are an important fungal molecular signal that plants recognize through the chitin receptors CEBiP and CERK1 found on the plasma membrane. These receptors are in the LysM class of receptors and recognize the size and the acetylation of COs from fungi. Lipo-chitooligosaccharides (LCOs) are another important molecular signal produced by both bacteria and fungi that are recognized by other LysM receptors. 
     In addition to benign and pathogenic microbes, some microbes can be beneficial to plants through association or symbiosis. Plants that enter into symbiotic relationships with certain nitrogen fixing bacteria and fungi need to be able to recognize the specific bacterial or fungal species to initiate the symbiosis while still being able to activate their immune systems to respond to other bacteria and fungi. One important mechanism that allows plants to recognize these specific bacteria or fungi is through specialized LysM receptors that have high affinity and high selectivity for the form of LCOs produced by the specific bacteria or fungi while LCOs from other bacteria and fungi are not recognized by these specialized LysM receptors. 
     Functional studies using mutant plants and phenotypic outputs have been used to identify these specialized LysM receptors. At present, however, only a few high affinity and high selectivity LysM receptors from a limited number of plant species and able to recognize a limited number of potential symbionts have been experimentally identified. As these receptors are required for recognizing symbiotic bacterial and fungal species, and for initiating symbiosis, it will be important for more receptors to be available that can be used to engineer recognition of additional symbiotic bacterial and fungal species. A broader range of receptors is needed both for engineering symbiosis in plants not currently able to form symbiotic relationships and for optimizing symbiosis in plants able to form symbiotic relationships. 
     BRIEF SUMMARY 
     There exists a clear need for additional specialized LysM receptors in order to engineer plant-microbial symbiotic relationships. Accordingly, the present disclosure provides multiple new high affinity and high selectivity LysM receptors that allow plants to recognize lipo-chitooligosaccharides (LCOs) produced by bacterial or fungal species. 
     Certain aspects of the present disclosure relate to a genetically altered plant or plant part containing a nucleic acid sequence encoding a heterologous receptor polypeptide, wherein the heterologous receptor polypeptide is selected from the group of a first polypeptide with at least 70% sequence identity, at least 75% sequence identity, at least 80% sequence identity, at least 85% sequence identity, at least 90% sequence identity, at least 95% sequence identity, at least 96% sequence identity, at least 97% sequence identity, at least 98% sequence identity, or at least 99% sequence identity to SEQ ID NO:5 [chickpea/ Cicer arietinum  NFR5], a second polypeptide with at least 70% sequence identity, at least 75% sequence identity, at least 80% sequence identity, at least 85% sequence identity, at least 90% sequence identity, at least 95% sequence identity, at least 96% sequence identity, at least 97% sequence identity, at least 98% sequence identity, or at least 99% sequence identity to SEQ ID NO:7 [bean/ Phaseolus vulgaris  NFR5], a third polypeptide with at least 70% sequence identity, at least 75% sequence identity, at least 80% sequence identity, at least 85% sequence identity, at least 90% sequence identity, at least 95% sequence identity, at least 96% sequence identity, at least 97% sequence identity, at least 98% sequence identity, or at least 99% sequence identity to SEQ ID NO:9 [peanut/ Arachis  NFR5], a fourth polypeptide with at least 70% sequence identity, at least 75% sequence identity, at least 80% sequence identity, at least 85% sequence identity, at least 90% sequence identity, at least 95% sequence identity, at least 96% sequence identity, at least 97% sequence identity, at least 98% sequence identity, or at least 99% sequence identity to SEQ ID NO:11 [ Lotus  LYS11], a fifth polypeptide with at least 70% sequence identity, at least 75% sequence identity, at least 80% sequence identity, at least 85% sequence identity, at least 90% sequence identity, at least 95% sequence identity, at least 96% sequence identity, at least 97% sequence identity, at least 98% sequence identity, or at least 99% sequence identity to SEQ ID NO:12 [ Medicago  LYR1], a sixth polypeptide with at least 70% sequence identity, at least 75% sequence identity, at least 80% sequence identity, at least 85% sequence identity, at least 90% sequence identity, at least 95% sequence identity, at least 96% sequence identity, at least 97% sequence identity, at least 98% sequence identity, or at least 99% sequence identity to SEQ ID NO:13 [ Parasponia  NFP1], a seventh polypeptide with at least 70% sequence identity, at least 75% sequence identity, at least 80% sequence identity, at least 85% sequence identity, at least 90% sequence identity, at least 95% sequence identity, at least 96% sequence identity, at least 97% sequence identity, at least 98% sequence identity, or at least 99% sequence identity to SEQ ID NO:16 [barley HvLysM-RLK1 (AK370300)], an eighth polypeptide with at least 70% sequence identity, at least 75% sequence identity, at least 80% sequence identity, at least 85% sequence identity, at least 90% sequence identity, at least 95% sequence identity, at least 96% sequence identity, at least 97% sequence identity, at least 98% sequence identity, or at least 99% sequence identity to SEQ ID NO:17 [barley HvLysM-RLK2 (AK357612)], a ninth polypeptide with at least 70% sequence identity, at least 75% sequence identity, at least 80% sequence identity, at least 85% sequence identity, at least 90% sequence identity, at least 95% sequence identity, at least 96% sequence identity, at least 97% sequence identity, at least 98% sequence identity, or at least 99% sequence identity to SEQ ID NO:18 [barley HvLysM-RLK3 AK372128], a tenth polypeptide with at least 70% sequence identity, at least 75% sequence identity, at least 80% sequence identity, at least 85% sequence identity, at least 90% sequence identity, at least 95% sequence identity, at least 96% sequence identity, at least 97% sequence identity, at least 98% sequence identity, or at least 99% sequence identity to SEQ ID NO:19 [barley HvLysM-RLK10 (HORVU4Hr1 G066170)], an eleventh polypeptide with at least 70% sequence identity, at least 75% sequence identity, at least 80% sequence identity, at least 85% sequence identity, at least 90% sequence identity, at least 95% sequence identity, at least 96% sequence identity, at least 97% sequence identity, at least 98% sequence identity, or at least 99% sequence identity to SEQ ID NO:20 [maize ZM1 (XP 020399958)], a twelfth polypeptide with at least 70% sequence identity, at least 75% sequence identity, at least 80% sequence identity, at least 85% sequence identity, at least 90% sequence identity, at least 95% sequence identity, at least 96% sequence identity, at least 97% sequence identity, at least 98% sequence identity, or at least 99% sequence identity to SEQ ID NO:21 [maize ZM5 (XP 008652982.1)], a thirteenth polypeptide with at least 70% sequence identity, at least 75% sequence identity, at least 80% sequence identity, at least 85% sequence identity, at least 90% sequence identity, at least 95% sequence identity, at least 96% sequence identity, at least 97% sequence identity, at least 98% sequence identity, or at least 99% sequence identity to SEQ ID NO:22 [apple NFP5 XP 008338966.1], or a fourteenth polypeptide with at least 70% sequence identity, at least 75% sequence identity, at least 80% sequence identity, at least 85% sequence identity, at least 90% sequence identity, at least 95% sequence identity, at least 96% sequence identity, at least 97% sequence identity, at least 98% sequence identity, or at least 99% sequence identity to SEQ ID NO:23 [strawberry NFR5 XP 004300586.2]. In some embodiments, the heterologous receptor polypeptide is selected from the group of SEQ ID NO:5 [chickpea/ Cicer arietinum  NFR5], SEQ ID NO:7 [bean/ Phaseolus vulgaris  NFR5], SEQ ID NO:9 [peanut/ Arachis  NFR5], SEQ ID NO:11 [ Lotus  LYS11], SEQ ID NO:12 [ Medicago  LYR1], SEQ ID NO:13 [ Parasponia  NFP1], SEQ ID NO:16 [barley HvLysM-RLK1 (AK370300)], SEQ ID NO:17 [barley HvLysM-RLK2 (AK357612)], SEQ ID NO:18 [barley HvLysM-RLK3 AK372128], SEQ ID NO:19 [barley HvLysM-RLK10 (HORVU4Hr1G066170)], SEQ ID NO:20 [maize ZM1 (XP 020399958)], SEQ ID NO:21 [maize ZM5 (XP 008652982.1)], SEQ ID NO:22 [apple NFP5 XP 008338966.1], and SEQ ID NO:23 [strawberry NFR5 XP 004300586.2]. In some embodiments, the expression of the heterologous receptor polypeptide allows the plant or part thereof to recognize lipo-chitooligosaccharides (LCOs) through the heterologous receptor polypeptide. In some embodiments, the LCOs are produced by nitrogen-fixing bacteria or by mycorrhizal fungi. In some embodiments, the LCOs are produced by nitrogen-fixing bacteria selected from the group of  Mesorhizobium loti, Mesorhizobium huakuii, Mesorhizobium mediterraneum, Mesorhizobium ciceri, Mesorhizobium  spp.,  Rhizobium mongolense, Rhizobium tropici, Rhizobium etli phaseoli, Rhizobium giardinii, Rhizobium leguminosarum  optionally  R. leguminosarum trifolii, R. leguminosarum viciae , and  R. leguminosarum phaseoli, Burkholderiales  optionally symbionts of  Mimosa, Sinorhizobium meliloti, Sinorhizobium medicae, Sinorhizobium fredii, Sinorhizobium fredii  NGR234,  Azorhizobium caulinodans, Bradyrhizobium japonicum, Bradyrhizobium elkanii, Bradyrhizobium liaonginense, Rhizobium  spp.,  Mesorhizobium  spp.,  Sinorhizobium  spp.,  Azorhizobium  spp.  Frankia  spp., or any combination thereof, or by mycorrhizal fungi selected from the group of  Acaulosporaceae  spp.,  Diversisporaceae  spp.,  Gigasporaceae  spp.,  Pacisporaceae  spp.,  Funneliformis  spp.,  Glomus  spp.,  Rhizophagus  spp.,  Sclerocystis  spp.,  Septoglomus  spp.,  Claroideoglomus  spp.,  Ambispora  spp.,  Archaeospora  spp.,  Geosiphon pyriformis, Paraglomus  spp., other species in the division  Glomeromycota , or any combination thereof. In some embodiments, the heterologous polypeptide is localized to a plant cell plasma membrane. In some embodiments, the plant cell is a root cell. In some embodiments, the root cell is a root epidermal cell or a root cortex cell. In some embodiments, the heterologous polypeptide is expressed in a developing plant root system. In some embodiments, the nucleic acid sequence is operably linked to a promoter. In some embodiments, the promoter is a root specific promoter. In some embodiments, the promoter is selected from the group of a NFR1 or NFR5/NFP promoter, the  Lotus  NFR5 promoter (SEQ ID NO: 24) and the  Lotus  NFR1 promoters (SEQ ID NO:25) the maize allothioneine promoter, the chitinase promoter, the maize ZRP2 promoter, the tomato LeExtl promoter, the glutamine synthetase soybean root promoter, the RCC3 promoter, the rice antiquitine promoter, the LRR receptor kinase promoter, or the  Arabidopsis  pCO2 promoter. In some embodiments, the promoter is a constitutive promoter optionally selected from the group of the CaMV35S promoter, a derivative of the CaMV35S promoter, the maize ubiquitin promoter, the trefoil promoter, a vein mosaic cassava virus promoter, or the  Arabidopsis  UBQ10 promoter. In some embodiments, the plant is selected from the group of corn (e.g., maize,  Zea mays ), rice (e.g.,  Oryza sativa, Oryza glaberrima, Zizania  spp.), barley (e.g.,  Hordeum vulgare ), wheat (e.g., common wheat, spelt, durum,  Triticum aestivum, Triticum spelta, Triticum durum, Triticum  spp.),  Trema  spp. (e.g.,  Trema cannabina, Trema cubense, Trema discolor, Trema domingensis, Trema integerrima, Trema lamarckiana, Trema micrantha, Trema orientalis, Trema philippinensis, Trema strigilosa, Trema tomentosa ), apple (e.g.,  Malus pumila ), pear (e.g.,  Pyrus communis, Pyrus ×bretschneideri,  Pyrus pyrifolia, Pyrus sinkiangensis, Pyrus pashia, Pyrus  spp.), plum (e.g., prune, damson, bullaces,  Prunus domestica, Prunus  salicina), apricot (e.g.,  Prunus armeniaca, Prunus brigantina, Prunus mandshurica, Prunus mume, Prunus sibirica ), peach (e.g., nectarine,  Prunus persica ), almond (e.g.,  Prunus dulcis, Prunus amygdalus ), walnut (e.g., Persian walnut, English walnut, black walnut,  Juglans regia, Juglans nigra, Juglans cinerea, Juglans californica ), strawberry (e.g.,  Fragaria×ananassa, Fragaria chiloensis, Fragaria virginiana, Fragaria vesca ), raspberry (e.g., European red raspberry, black raspberry,  Rubus idaeus, Rubus occidentalis, Rubus strigosus ), blackberry (e.g., evergreen blackberry, Himalayan blackberry,  Rubus fruticosus, Rubus ursinus, Rubus laciniatus, Rubus argutus, Rubus armeniacus, Rubus plicatus, Rubus ulmifolius, Rubus allegheniensis ), red currant (e.g.,  Ribes rubrum, Ribes spicatum, Ribesbes alpinum, Ribes schlechtendalii, Ribes multiflorum, Ribes petraeum, Ribes triste ), black currant (e.g.,  Ribes nigrum ), melon (e.g., watermelon, winter melon, casabas, cantaloupe, honeydew, muskmelon,  Citrullus lanatus, Benincasa hispida, Cucumis melo cantalupensis, Cucumis melo inodorus, Cucumis melo reticulatus ), cucumber (e.g., slicing cucumbers, pickling cucumbers, English cucumber,  Cucumis sativus ), pumpkin (e.g.,  Cucurbita pepo, Cucurbita maxima ), squash (e.g., gourd,  Cucurbita argyrosperma, Cucurbita ficifolia, Cucurbita maxima, Cucurbita moschata ), grape (e.g.,  Vitis vinifera, Vitis amurensis, Vitis labrusca, Vitis mustangensis, Vitis riparia, Vitis rotundifolia ), or hemp (e.g.,  cannabis, Cannabis sativa ). 
     In some embodiments of any of the above embodiments, the plant part is a leaf, a stem, a root, a root primordia, a flower, a seed, a fruit, a kernel, a grain, a cell, or a portion thereof. In some embodiments, the part is a fruit, a kernel, or a grain. 
     In some aspects, the present disclosure relates to a pollen grain or an ovule of the genetically altered plant of any of the above embodiments. 
     In some aspects, the present disclosure relates to a protoplast produced from the plant of any of the above embodiments. 
     In some aspects, the present disclosure relates to a tissue culture produced from protoplasts or cells from the plant of any of the above embodiments, wherein the cells or protoplasts are produced from a plant part selected from the group consisting of leaf, anther, pistil, stem, petiole, root, root primordia, root tip, fruit, seed, flower, cotyledon, hypocotyl, embryo, and meristematic cell. 
     Certain aspects of the present disclosure relate to a method of producing the genetically altered plant of any of the above embodiments, comprising introducing a genetic alteration to the plant comprising the nucleic acid sequence. In some embodiments, the nucleic acid sequence is operably linked to a promoter. In some embodiments, the promoter is a root specific promoter. In some embodiments, the promoter is selected from the group of a NFR1 or NFR5/NFP promoter, the  Lotus  NFR5 promoter (SEQ ID NO: 24) and the  Lotus  NFR1 promoters (SEQ ID NO:25) the maize allothioneine promoter, the chitinase promoter, the maize ZRP2 promoter, the tomato LeExtl promoter, the glutamine synthetase soybean root promoter, the RCC3 promoter, the rice antiquitine promoter, the LRR receptor kinase promoter, or the  Arabidopsis  pCO2 promoter. In some embodiments, the promoter is a constitutive promoter optionally selected from the group of the CaMV35S promoter, a derivative of the CaMV35S promoter, the maize ubiquitin promoter, the trefoil promoter, a vein mosaic cassava virus promoter, or the  Arabidopsis  UBQ10 promoter. In some embodiments, the nucleic acid sequence is inserted into the genome of the plant so that the nucleic acid sequence is operably linked to an endogenous promoter. In some embodiments, the endogenous promoter is a root specific promoter. 
     In some aspects, the present disclosure relates to a genetically altered plant seed containing a nucleic acid sequence encoding a heterologous receptor polypeptide, wherein the heterologous receptor polypeptide is selected from the group of a first polypeptide with at least 70% sequence identity, at least 75% sequence identity, at least 80% sequence identity, at least 85% sequence identity, at least 90% sequence identity, at least 95% sequence identity, at least 96% sequence identity, at least 97% sequence identity, at least 98% sequence identity, or at least 99% sequence identity to SEQ ID NO:5 [chickpea/ Cicer arietinum  NFR5], a second polypeptide with at least 70% sequence identity, at least 75% sequence identity, at least 80% sequence identity, at least 85% sequence identity, at least 90% sequence identity, at least 95% sequence identity, at least 96% sequence identity, at least 97% sequence identity, at least 98% sequence identity, or at least 99% sequence identity to SEQ ID NO:7 [bean/ Phaseolus vulgaris  NFR5], a third polypeptide with at least 70% sequence identity, at least 75% sequence identity, at least 80% sequence identity, at least 85% sequence identity, at least 90% sequence identity, at least 95% sequence identity, at least 96% sequence identity, at least 97% sequence identity, at least 98% sequence identity, or at least 99% sequence identity to SEQ ID NO:9 [peanut/ Arachis  NFR5], a fourth polypeptide with at least 70% sequence identity, at least 75% sequence identity, at least 80% sequence identity, at least 85% sequence identity, at least 90% sequence identity, at least 95% sequence identity, at least 96% sequence identity, at least 97% sequence identity, at least 98% sequence identity, or at least 99% sequence identity to SEQ ID NO:11 [ Lotus  LYS11], a fifth polypeptide with at least 70% sequence identity, at least 75% sequence identity, at least 80% sequence identity, at least 85% sequence identity, at least 90% sequence identity, at least 95% sequence identity, at least 96% sequence identity, at least 97% sequence identity, at least 98% sequence identity, or at least 99% sequence identity to SEQ ID NO:12 [ Medicago  LYR1], a sixth polypeptide with at least 70% sequence identity, at least 75% sequence identity, at least 80% sequence identity, at least 85% sequence identity, at least 90% sequence identity, at least 95% sequence identity, at least 96% sequence identity, at least 97% sequence identity, at least 98% sequence identity, or at least 99% sequence identity to SEQ ID NO:13 [ Parasponia  NFP1], a seventh polypeptide with at least 70% sequence identity, at least 75% sequence identity, at least 80% sequence identity, at least 85% sequence identity, at least 90% sequence identity, at least 95% sequence identity, at least 96% sequence identity, at least 97% sequence identity, at least 98% sequence identity, or at least 99% sequence identity to SEQ ID NO:16 [barley HvLysM-RLK1 (AK370300)], an eighth polypeptide with at least 70% sequence identity, at least 75% sequence identity, at least 80% sequence identity, at least 85% sequence identity, at least 90% sequence identity, at least 95% sequence identity, at least 96% sequence identity, at least 97% sequence identity, at least 98% sequence identity, or at least 99% sequence identity to SEQ ID NO:17 [barley HvLysM-RLK2 (AK357612)], a ninth polypeptide with at least 70% sequence identity, at least 75% sequence identity, at least 80% sequence identity, at least 85% sequence identity, at least 90% sequence identity, at least 95% sequence identity, at least 96% sequence identity, at least 97% sequence identity, at least 98% sequence identity, or at least 99% sequence identity to SEQ ID NO:18 [barley HvLysM-RLK3 AK372128], a tenth polypeptide with at least 70% sequence identity, at least 75% sequence identity, at least 80% sequence identity, at least 85% sequence identity, at least 90% sequence identity, at least 95% sequence identity, at least 96% sequence identity, at least 97% sequence identity, at least 98% sequence identity, or at least 99% sequence identity to SEQ ID NO:19 [barley HvLysM-RLK10 (HORVU4Hr1 G066170)], an eleventh polypeptide with at least 70% sequence identity, at least 75% sequence identity, at least 80% sequence identity, at least 85% sequence identity, at least 90% sequence identity, at least 95% sequence identity, at least 96% sequence identity, at least 97% sequence identity, at least 98% sequence identity, or at least 99% sequence identity to SEQ ID NO:20 [maize ZM1 (XP 020399958)], a twelfth polypeptide with at least 70% sequence identity, at least 75% sequence identity, at least 80% sequence identity, at least 85% sequence identity, at least 90% sequence identity, at least 95% sequence identity, at least 96% sequence identity, at least 97% sequence identity, at least 98% sequence identity, or at least 99% sequence identity to SEQ ID NO:21 [maize ZM5 (XP 008652982.1)], a thirteenth polypeptide with at least 70% sequence identity, at least 75% sequence identity, at least 80% sequence identity, at least 85% sequence identity, at least 90% sequence identity, at least 95% sequence identity, at least 96% sequence identity, at least 97% sequence identity, at least 98% sequence identity, or at least 99% sequence identity to SEQ ID NO:22 [apple NFP5 XP_008338966.1], or a fourteenth polypeptide with at least 70% sequence identity, at least 75% sequence identity, at least 80% sequence identity, at least 85% sequence identity, at least 90% sequence identity, at least 95% sequence identity, at least 96% sequence identity, at least 97% sequence identity, at least 98% sequence identity, or at least 99% sequence identity to SEQ ID NO:23 [strawberry NFR5 XP_004300586.2]. In some embodiments, the heterologous receptor polypeptide is selected from the group of SEQ ID NO:5 [chickpea/ Cicer arietinum  NFR5], SEQ ID NO:7 [bean/ Phaseolus vulgaris  NFR5], SEQ ID NO:9 [peanut/ Arachis  NFR5], SEQ ID NO:11 [ Lotus  LYS11], SEQ ID NO:12 [ Medicago  LYR1], SEQ ID NO:13 [ Parasponia  NFP1], SEQ ID NO:16 [barley HvLysM-RLK1 (AK370300)], SEQ ID NO:17 [barley HvLysM-RLK2 (AK357612)], SEQ ID NO:18 [barley HvLysM-RLK3 AK372128], SEQ ID NO:19 [barley HvLysM-RLK10 (HORVU4Hr1G066170)], SEQ ID NO:20 [maize ZM1 (XP_020399958)], SEQ ID NO:21 [maize ZM5 (XP_008652982.1)], SEQ ID NO:22 [apple NFP5 XP_008338966.1], or SEQ ID NO:23 [strawberry NFR5 XP_004300586.2]. In some embodiments, the expression of the heterologous receptor polypeptide allows the plant or part thereof to recognize lipo-chitooligosaccharides (LCOs) through the heterologous receptor polypeptide. In some embodiments, the LCOs are produced by nitrogen-fixing bacteria or by mycorrhizal fungi. In some embodiments, the LCOs are produced by nitrogen-fixing bacteria selected from the group of  Mesorhizobium loti, Mesorhizobium huakuii, Mesorhizobium mediterraneum, Mesorhizobium ciceri, Mesorhizobium  spp.,  Rhizobium mongolense, Rhizobium tropici, Rhizobium etli phaseoli, Rhizobium giardinii, Rhizobium leguminosarum  optionally  R. leguminosarum trifolii, R. leguminosarum viciae , and  R. leguminosarum phaseoli, Burkholderiales  optionally symbionts of  Mimosa, Sinorhizobium meliloti, Sinorhizobium medicae, Sinorhizobium fredii, Sinorhizobium fredii  NGR234,  Azorhizobium caulinodans, Bradyrhizobium japonicum, Bradyrhizobium elkanii, Bradyrhizobium liaonginense, Rhizobium  spp.,  Mesorhizobium  spp.,  Sinorhizobium  spp.,  Azorhizobium  spp.  Frankia  spp., or any combination thereof, or by mycorrhizal fungi selected from the group of  Acaulosporaceae  spp.,  Diversisporaceae  spp.,  Gigasporaceae  spp.,  Pacisporaceae  spp.,  Funneliformis  spp.,  Glomus  spp.,  Rhizophagus  spp.,  Sclerocystis  spp.,  Septoglomus  spp.,  Claroideoglomus  spp.,  Ambispora  spp.,  Archaeospora  spp.,  Geosiphon  pyriformis,  Paraglomus  spp., other species in the division  Glomeromycota , or any combination thereof. In some embodiments, the heterologous polypeptide is localized to a plant cell plasma membrane when the seed is grown into a plant. In some embodiments, the plant cell is a root cell. In some embodiments, the root cell is a root epidermal cell or a root cortex cell. In some embodiments, the heterologous polypeptide is expressed in a developing plant root system when the seed is grown into a plant. In some embodiments, the nucleic acid sequence is operably linked to a promoter. In some embodiments, the promoter is a root specific promoter. In some embodiments, the promoter is selected from the group of a NFR1 or NFR5/NFP promoter, the  Lotus  NFR5 promoter (SEQ ID NO: 24) and the  Lotus  NFR1 promoters (SEQ ID NO:25) the maize allothioneine promoter, the chitinase promoter, the maize ZRP2 promoter, the tomato LeExtl promoter, the glutamine synthetase soybean root promoter, the RCC3 promoter, the rice antiquitine promoter, the LRR receptor kinase promoter, or the  Arabidopsis  pCO2 promoter. In some embodiments, the promoter is a constitutive promoter optionally selected from the group of the CaMV35S promoter, a derivative of the CaMV35S promoter, the maize ubiquitin promoter, the trefoil promoter, a vein mosaic cassava virus promoter, or the  Arabidopsis  UBQ10 promoter. In some embodiments, the plant is selected from the group of corn (e.g., maize,  Zea mays ), rice (e.g.,  Oryza sativa, Oryza glaberrima, Zizania  spp.), barley (e.g.,  Hordeum vulgare ), wheat (e.g., common wheat, spelt, durum,  Triticum aestivum, Triticum spelta, Triticum durum, Triticum  spp.),  Trema  spp. (e.g.,  Trema cannabina, Trema cubense, Trema discolor, Trema domingensis, Trema integerrima, Trema lamarckiana, Trema micrantha, Trema orientalis, Trema philippinensis, Trema strigilosa, Trema tomentosa ), apple (e.g.,  Malus pumila ), pear (e.g.,  Pyrus communis, Pyrus xbretschneideri, Pyrus pyrifolia, Pyrus sinkiangensis, Pyrus pashia, Pyrus  spp.), plum (e.g., prune, damson, bullaces,  Prunus domestica, Prunus salicina ), apricot (e.g.,  Prunus armeniaca, Prunus brigantina, Prunus mandshurica, Prunus mume, Prunus sibirica ), peach (e.g., nectarine,  Prunus persica ), almond (e.g.,  Prunus dulcis, Prunus amygdalus ), walnut (e.g., Persian walnut, English walnut, black walnut,  Juglans regia, Juglans nigra, Juglans cinerea, Juglans californica ), strawberry (e.g.,  Fragaria×ananassa, Fragaria chiloensis, Fragaria virginiana, Fragaria vesca ), raspberry (e.g., European red raspberry, black raspberry,  Rubus idaeus, Rubus occidentalis, Rubus strigosus ), blackberry (e.g., evergreen blackberry, Himalayan blackberry,  Rubus fruticosus, Rubus ursinus, Rubus laciniatus, Rubus argutus, Rubus armeniacus, Rubus plicatus, Rubus ulmifolius, Rubus allegheniensis ), red currant (e.g.,  Ribes rubrum, Ribes spicatum , Rib esbes  alpinum, Ribes schlechtendalii, Ribes multiflorum, Ribes petraeum, Ribes triste ), black currant (e.g.,  Ribes nigrum ), melon (e.g., watermelon, winter melon, casabas, cantaloupe, honeydew, muskmelon,  Citrullus lanatus, Benincasa hispida, Cucumis melo cantalupensis, Cucumis melo inodorus, Cucumis melo reticulatus ), cucumber (e.g., slicing cucumbers, pickling cucumbers, English cucumber,  Cucumis sativus ), pumpkin (e.g.,  Cucurbita pepo, Cucurbita maxima ), squash (e.g., gourd,  Cucurbita argyrosperma, Cucurbita ficifolia, Cucurbita maxima, Cucurbita moschata ), grape (e.g.,  Vitis vinifera, Vitis amurensis, Vitis labrusca, Vitis mustangensis, Vitis riparia, Vitis rotundifolia ), or hemp (e.g.,  cannabis, Cannabis sativa ). 
     In some aspects, the present disclosure relates to a plant produced from the genetically altered plant seed of any one of the above embodiments, wherein the plant the plant expresses the heterologous polypeptide, and wherein the expression of the heterologous polypeptide allows the plant to recognize lipo-chitooligosaccharides (LCOs) through the heterologous receptor polypeptide. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A-1B  show the structure of the NFP receptor ectodomain (NFP-ECD).  FIG. 1A  shows a NFP-ECD with the three LysM domains labeled (LysM1, LysM2, and LysM3). Motifs within the LysM domains are also labeled: LysM1 motifs=α1, α2, β1, and β2; LysM2 motifs=α3, α4, β3, and β4; and LysM3 motifs=α5, α6, β5, and β6. Glycosylations (di-GlcNAc cores are shown (projecting from α1 at upper; additional cores visible at center adjacent to (32 and 31 as well as at bottom left behind α4), and disulfide bridges are indicated with arrows and labeled with the residue numbers (C47-C166; C39-C104; and C102-C164).  FIG. 1B  shows SAXS envelope of NFP-ECD showing a rigid stalk region of the receptor. The overall dimensions are shown in angstrom (Å). 
         FIGS. 2A-2B  show biolayer interferometry (BLI) binding curves using  S. meliloti  LCO-IV and LCO-V, and  M. loti  LCO-V and C06.  FIG. 2A  shows NFP binds  S. meliloti  LCO-IV ( S. meliloti  Nod-LCO-IV) with an average K D  of 26±0.2 μM, and that NFP binds  S. meliloti  LCO-V ( S. meliloti  Nod-LCO-V) with an average K D  of 32±0.2 μM. The results shown in  FIG. 2A  are from seven replicates.  FIG. 2B  shows NFP does not bind  M. loti  LCO-V ( M. loti  Nod-LCO-V) and  M. loti  C06. The results shown in  FIG. 2B  are from six replicates. 
         FIGS. 3A-3B  show  S. meliloti  LCO-IV mutants, and the results of binding assays using these variants.  FIG. 3A  shows a schematic of  S. meliloti  LCO-IV mutants with arrows indicating the locations that are affected in LCO-IV by each of the four mutations NodL, NodH, NodFE, and NodFL.  FIG. 3B  shows binding assays performed using three LCO-IV mutants and  S. meliloti  LCO-IV as a control. The results shown for LCO-IV are from seven replicates, the results shown for NodH ( S. meliloti  ΔH) are from four replicates, the results shown for NodFE ( S. meliloti  AFE) are from three replicates, and the results shown for NodFL ( S. meliloti  AFL) are from three replicates. 
         FIGS. 4A-4B  show the hydrophobic patch in the  Medicago  NFP LysM2 domain, and binding assay measurements using mutants of important residues within the hydrophobic patch.  FIG. 4A  shows molecular docking of C04 (designated as “Ligand”) onto  Medicago  NFP shaded with electrostatic surface potential. The hydrophobic patch is circled by a dashed black line, and the locations of important residues L147 and L154 are shown using arrows. The position of the LCO fatty-acid is depicted with a dashed grey line.  FIG. 4B  shows binding assay measurements comparing a wild type (WT) NFP (“NFP WT”) with an NFP mutated at residues 147 and 154 (“NFP L147D L154D”; bold). The results shown for NFP WT are from seven replicates and the results shown for NFP L147D L154D are from four replicates. 
         FIG. 5  shows the general schematic of the construct used for mutant complementation experiments. Designations are as follows: T-DNA left border sequence=LB, T-DNA right border sequence=RB, β-glucuronidase gene=GUS, buffer sequence=buffer, early nodulin-11 precursor promoter=pEnod11, NFP promoter=pNfp. The arrows indicate the directions of gene transcription. 
         FIGS. 6A-6B  show complementation assays of  Medicago  nfp mutants.  FIG. 6A  shows complementation tested by inoculation with  S. meliloti  strain 2011; columns represent the mean nodule numbers after 49 dpi.  FIG. 6B  shows complementation tested by inoculation with  S. medicae ; columns represent the mean nodule numbers after 28 dpi. For  FIGS. 6A-6B , circles represent the individual counts; empty circles= Medicago  Jemalong wild type background (WT); filled circles= Medicago  nfp mutant background (nfp); EVC=empty vector control; WT=wild type NFP control; error bars show the SEM; different letters indicate significant differences among the samples (ANOVA, Tukey, P&lt;0.05); and number of plants assayed indicated at labels on x-axis in parentheses. 
         FIGS. 7A-7G  show homology modelling of other LCO receptor ectodomains with surface representations of different LCO receptors shaded according to their electrostatic potential. When present, the hydrophobic patch is circled by a dashed black line, and a negative patch is circled by a dashed grey line. The docked ligand (chitin) is shown as guidance.  FIG. 7A  shows homology modelling of other characterized LCO receptors:  Lotus  NFR5, pea ( Pisum sativum ) SYM10, and soybean ( Glycine max ) NFR5a.  FIG. 7B  shows homology modelling of the previously uncharacterized LCO receptor homologues in chickpea ( Cicer arietinum ) NFR5, bean ( Phaseolus vulgaris ) NFR5, and peanut ( Arachis hypogaea ) NFR5, which have a hydrophobic patch.  FIG. 7C-7E  show homology modelling of more distantly related receptors including ( FIG. 7C ) LYS receptors: LYS11, LYS12, LYS13, LYS14, LYS15, LYS16, LYS17, and LYS18; ( FIG. 7D ) LYR receptors: LYR1, LYR2, LYR3, and LYR4, and ( FIG. 7E ) NFP receptors:  Parasponia  NFP1 and  Parasponia  NFP2.  FIG. 7F  shows models of  Medicago  LYR3 and  Lotus  LYS12 receptors that have no hydrophobic patch (models viewed from the LysM3 domain and with docked ligand (chitin).  FIG. 7G  shows a comparison of the  Lotus  LYS11 model (LYS11—model; left; also in  FIG. 7C ) with the crystal structure of  Lotus  LYS11 (LYS11—crystal structure; right). 
         FIGS. 8A-8C  show an alignment of selected LysM receptors from  Arabidopsis thaliana  (At; AT3G21630 CERK1 (SEQ ID NO: 37), AT1G77630 LYP3 (SEQ ID NO: 42), AT2G17120_LYP1 (SEQ ID NO: 44)),  Zea mays  (Zm; ZM9 NP 001146346.1 (SEQ ID NO: 34)),  Hordeum vulgare  (Hv; HvLysMRLK4 AK369594.1 (SEQ ID NO: 35)),  Medicago truncatula  (Mt or Medtr; Mt_LYK9 XP_003601376 (SEQ ID NO: 31), Mt_LYK3_XP_003616958 (SEQ ID NO: 33), Mt_LYK10 XP_003613165 (SEQ ID NO: 39), Medtr5g042440.1 (SEQ ID NO: 41)),  Oryza sativa  (Os; XP_015611967_OsCERK1 (SEQ ID NO: 36), OsCeBiP (SEQ ID NO: 43)) and  Lotus japonicus  (Lj; BAI79273.1_CERK6 (SEQ ID NO: 30), CAE02590.1_NFR1 (SEQ ID NO: 32), BAI79284.1_EPR3 (SEQ ID NO: 38), CAE02597.1 NFR5 (SEQ ID NO: 40)). NFR1 and NFR5 are Nod factor receptors, EPR3 is an exopolysaccharide receptor, AtLYP1 and AtLYP3 are peptidoglycan receptors, AtCERK1, OsCERK1, OsCeBIP, CERK6 are chitooligosaccharide receptors. C(x)XXXC and CxC motifs flanking the three LysM domains are shown. LysM1 (black line), LysM2 (grey line) and LysM3 (grey line) are shown.  FIG. 8A  shows the first two portions of the alignment including all of the LysM1 domain and part of the LysM2 domain.  FIG. 8B  shows the third and fourth portions of the alignment including the rest of the LysM2 domain and all of the LysM3 domain.  FIG. 8C  shows the fifth portion of the alignment. 
         FIGS. 9A-9B  show an alignment of selected LysM receptors from  Arabidopsis thaliana  (At; AT3G21630 CERK1 (SEQ ID NO: 37)),  Zea mays  (Zm; XP_020399958_ZM1 (SEQ ID NO: 20), XP_008652982.1_ZM5 (SEQ ID NO: 21), AQK73561.1_ZM7 (SEQ ID NO: 46), NP_001147981.1_ZM3 (SEQ ID NO: 47), NP_001147941.2_ZM6 (SEQ ID NO: 48), AQK58792.1_ZM4 (SEQ ID NO: 49), ZM9 NP_001146346.1 (SEQ ID NO: 34)),  Hordeum vulgare  (Hv; HORVU4Hr1 G066170_HvLysMRLK10 (SEQ ID NO: 19), AK357612_HvLysMRLK2 (SEQ ID NO: 17), AK370300_HvLysmRLK1 (SEQ ID NO: 16), AK372128_HvLysMRLK3 (SEQ ID NO: 18), HvLysMRLK4_AK369594.1 (SEQ ID NO: 35)),  Oryza sativa  (Os; XP_015611967_OsCERK1 (SEQ ID NO: 36)),  Medicago truncatula  (Mt; XP_003613904.2_MtNFP (SEQ ID NO: 45), Mt_LYK3_XP_003616958 (SEQ ID NO: 33), Mt_LYK9_XP_003601376 (SEQ ID NO: 31)), and  Lotus japonicus  (Lj; CAE02590.1 NFR1 (SEQ ID NO: 32), CAE02597.1 NFR5 (SEQ ID NO: 40), BAI79273.1 CERK6 (SEQ ID NO: 30),). LjNFR1, LjNFR5, MtLYK3 and MtNFP are functional Nod factor receptors, AtCERK1, OsCERK1, LjCERK6 are functional chitin receptors. C(x)XXXC and CxC motifs flanking the three LysM domains are shown. LysM1 (black line), LysM2 (grey line) and LysM3 (grey line) are shown. The number of “X” residues in the C(x)XXXC motif located before LysM1 varies between receptors and therefore the location of LysM1 (black line) changes accordingly in the alignments in this figure and in successive figures.  FIG. 9A  shows the first and second portions of the alignment including all of the LysM1 domain and part of the LysM2 domain.  FIG. 9B  shows the third and fourth portions of the alignment including the rest of the LysM2 domain and all of the LysM3 domain. 
         FIGS. 10A-10B  show an alignment of selected LysM receptors from  Zea mays  (Zm; ONM41523.1_ZM8 (SEQ ID NO: 50), XP_008657477.1_ZM2 (SEQ ID NO: 51), Zm00001d043516_ZM10 (SEQ ID NO: 53)),  Hordeum vulgare  (Hv; MLOC 5489.2_HvLysM-RLK9 (SEQ ID NO: 52), MLOC_18610.1_HvLysM-RLK8 (SEQ ID NO: 54), MLOC_57536.1 HvLysM-RLK6 (SEQ ID NO: 55)),  Medicago truncatula  (Mt; Mt_LYK10 XP_003613165 (SEQ ID NO: 39), Mt_LYK3 XP_003616958 (SEQ ID NO: 33), XP_003613904.2 MtNFP (SEQ ID NO: 45)), and  Lotus japonicus  (Lj; BAI79284.1 EPR3 (SEQ ID NO: 38), CAE02590.1 NFR1 (SEQ ID NO: 32), CAE02597.1 NFR5 (SEQ ID NO: 40)). LjNFR1, LjNFR5, MtLYK3 and MtNFP are functional Nod factor receptors, LjEPR3 is functional EPS receptor. C(x)XXXC and CxC motifs flanking the three LysM domains are shown. LysM1 (black line), LysM2 (grey line) and LysM3 (grey line) are shown.  FIG. 10A  shows the first, second, and third portions of the alignment including all of the LysM1 domain and all of the LysM2 domain.  FIG. 10B  shows the fourth, fifth, and sixth portions of the alignment including all of the LysM3 domain. 
         FIGS. 11A-11B  show an alignment of selected LysM receptors from  Arabidopsis thaliana  (At; AT1G21880.2 LYP2 (SEQ ID NO: 56), AT1G77630 LYP3 (SEQ ID NO: 42), AT2G17120_LYP1 (SEQ ID NO: 44)),  Oryza sativa  (Os; OsCeBiP (SEQ ID NO: 43)), and  Lotus japonicus  (Lj; LjLYP1 (SEQ ID NO: 57), LjLYP2 (SEQ ID NO: 58), LjLYP3 (SEQ ID NO: 58), CAE02590.1 NFR1 (SEQ ID NO: 32), CAE02597.1 NFR5 (SEQ ID NO: 40)). LjNFR1, LjNFR5, are functional Nod factor receptors, AtLYP2 and AtLYP3, are PGN receptors, OsCeBiP is a functional chitin receptor. C(x)XXXC and CxC motifs flanking the three LysM domains are shown. LysM1 (black line), LysM2 (grey line) and LysM3 (grey line) are shown.  FIG. 11A  shows the first, second, third, and fourth portions of the alignment including all of the LysM1 domain, all of the LysM2 domain, and all of the LysM3 domain.  FIG. 11B  shows the fifth, sixth, and seventh portions of the alignment. 
         FIGS. 12A-12E  show annotated amino acid sequences of previously known LCO receptors and newly identified LCO receptors.  FIG. 12A  shows the annotation key; the LysM1 domain is shown with a dashed underline, the LysM2 domain is shown with a solid underline, the hydrophobic patch residues are shown in bold, and the LysM3 domain is shown with residues italicized.  Medicago  NFP (MtNFP/1-595; SEQ ID NO: 1),  Lotus  NFR5 (a known LCO receptor; LjNFR5/1-595; SEQ ID NO: 2), Pea SYM10 (a known LCO receptor; Pea SYM10/1-594; SEQ ID NO: 3), and Soybean NFR5a (a known LCO receptor; GmNFR5a/1-598 max; SEQ ID NO: 4) are shown.  FIG. 12B  shows Chickpea NFR5 (a new LCO receptor; ChickpeaNFR5/1-557 ( Cicer arietinum ); SEQ ID NO: 5), Bean NFR5 (a new LCO receptor; BeanNFR5/1-597 ( Phaseolus vulgaris ); SEQ ID NO: 7), Peanut NFR5 (a new LCO receptor; PeanutNFR5/1-595 [ Arachis hypogaea  subsp.  hypogaea ]; SEQ ID NO: 9), and Lotus Lys11 (a new LCO receptor; LjLys11/1-591; SEQ ID NO: 11).  FIG. 12C  shows  Medicago  LYR1 (a new LCO receptor; MtLYR1/1-590; SEQ ID NO: 12),  Parasponia  NFP1 (a new LCO receptor; PanNFP1/1-613; SEQ ID NO: 13),  Parasponia  NFP2 (a known LCO receptor; PanNFP2/1-582; SEQ ID NO: 14), and Barley receptor HvLysM-RLK1 (a new LCO receptor; HvLysM-RLK1 (AK370300); SEQ ID NO: 16).  FIG. 12D  shows Barley receptor HvLysM-RLK2 (a new LCO receptor; HvLysM-RLK2 (AK357612); SEQ ID NO: 17), Barley receptor HvLysM-RLK3 AK372128 (a new LCO receptor; HvLysM-RLK3 AK372128; SEQ ID NO: 18), Barley receptor HvLysM-RLK10 (a new LCO receptor; HvLysM-RLK10 (HORVU4Hr1 G066170); SEQ ID NO: 19), and Maize receptor ZM1 (a new LCO receptor; ZM1 (XP_020399958); SEQ ID NO: 20).  FIG. 12E  shows Maize receptor ZM5 (a new LCO receptor; ZM5 (XP_008652982.1); SEQ ID NO: 21), Apple NFP5 (a new LCO receptor; XP_008338966.1 PREDICTED: serine/threonine receptor-like kinase NFP [ Malus domestica ]; SEQ ID NO: 22), and Strawberry NFR5 (a new LCO receptor; XP_004300586.2 PREDICTED: protein LYK5-like [ Fragaria vesca  subsp.  vesca ]; SEQ ID NO: 23). 
         FIGS. 13A-13D  show homology modelling of the barley RLK10 receptor (HvRLK10) ectodomain and results of binding experiments using the HvRLK10 ectodomain.  FIG. 13A  shows a schematic of the purified HvRLK10 ectodomain at the top (N-terminus=N′; LysM1=M1; LysM2=M2; LysM3=M3; 6×HIS tag used for purification=6×HIS; C-terminus=C′) and the results of binding assays of HvRLK10 ectodomain with C05 at the bottom.  FIG. 13B  shows homology modelling of the barley receptor RLK10 (HvRLK10) ectodomain with surface representation shaded according to its electrostatic potential. The hydrophobic patch is circled by a dashed black line, and a CO ligand is shown at the top of the hydrophobic patch.  FIG. 13C  shows the results of binding assays of HvRLK10 ectodomain with  M. loti  LCO.  FIG. 13D  shows the results of binding assays of HvRLK10 ectodomain with  S. meliloti  LCO. For  FIGS. 13A, and 13C-13D , binding in nm is shown on the y-axes, time in seconds (s) is shown on the x-axes, and the tested molecules are shown in the titles of the graphs (C05,  M. loti  LCO, and  S. meliloti  LCO). 
         FIGS. 14A-14C  show SAXS analyses of deglycosylated NFP-ECD and of glycosylated NFP-ECD, and dimensionless Kratky plots for deglycosylated NFP-ECD and glycosylated NFP-ECD.  FIG. 14A  shows SAXS analysis showing scattering curves with model fit (c2; left graph), Guinier plot (top middle graph), and P(r) distance distribution plot with Dmax indicated (bottom middle graph) for deglycosylated NFP-ECD, as well as the NFP-ECD crystal structure docked into the SAXS envelope for deglycosylated NFP-ECD (shows an extended stem-like structure; overall dimensions are shown in angstrom (Å)).  FIG. 14B  shows SAXS analysis showing scattering curves with model fit (c2; left graph), Guinier plot (top middle graph), and P(r) distance distribution plot with Dmax indicated (bottom middle graph) for glycosylated NFP-ECD, as well as the NFP-ECD crystal structure docked into the SAXS envelope for glycosylated NFP-ECD (shows an extended stem-like structure; overall dimensions are shown in angstrom (Å)).  FIG. 14C  shows the dimensionless Kratky plot (Rg based, Guinier and Vc based) for deglycosylated NFP-ECD (grey) and glycosylated NFP-ECD (light grey). 
         FIGS. 15A-15E  show BLI binding curves for NFP-ECD binding to  S. meliloti  LCO-V,  M. loti  LCO-V and Chitin (chitopentaose; C05).  FIG. 15A  shows NFP-ECD binds  S. meliloti  LCO-V with an average K d  of 22.3±0.1 μM (goodness of fit is described by the global fit R 2  on the mean value of each point=0.99; n=7).  FIG. 15B  shows NFP-ECD binds  M loti  LCO-V with a K d  that cannot be fitted because binding is too weak (n=6).  FIG. 15C  shows NFP-ECD does not bind chitin (n=6).  FIG. 15D  shows a table of BLI binding curve results for NFP-ECD binding to  S. meliloti  LCO-IV and LCO-IV variants.  FIG. 15E  shows BLI binding curve results for NFP-ECD binding to  S. meliloti  LCO-IV and LCO-IV variants. For  FIGS. 15A-15C and 15E , seven 2-fold dilution series of analyte (1.56-100 μM) were used for each experiment; experimental binding curves are represented in solid lines, fitting curves in dashed lines; and number of replicates performed using independent protein preparations (n) are indicated. For  FIGS. 15D-15E , LCO-IV variants shown in  FIG. 3A  and goodness of fit described by the global fit R 2  on the mean value of each point. 
         FIGS. 16A-16D  show BLI binding curves for WT NFP-ECD and hydrophobic patch mutant NFP-ECD (L147D/L154D) binding to  S. meliloti  LCO-IV and a schematic of the NFP receptor.  FIG. 16A  shows WT NFP-ECD binding to  S. meliloti  LCO-IV.  FIG. 16B  shows L147D/L154D NFP-ECD binding to  S. meliloti  LCO-IV. For  FIGS. 16A-16B , seven 2-fold dilution series of analyte (1.56-100 μM) were used for each experiment; and experimental binding curves are represented in solid lines, fitting curves in dashed lines.  FIG. 16C  shows a table summarizing the kinetic parameters of  FIGS. 16A-16B , with goodness of fit described by the global fit R 2  on the mean value of each point, and number of replicates performed using independent protein preparations (n) indicated.  FIG. 16D  shows a schematic of the NFP receptor with LysM1, LysM2, LysM3, stem, and transmembrane (TM) and kinase domains labeled, and the location of the hydrophobic patch in LysM2 indicated by a grey bar. Numbers below the schematic provide the corresponding amino acid residues, and the locations of the CxC motifs flanking the LysM domains are shown. 
         FIGS. 17A-17B  show BLI binding curves for  A. thaliana  CERK1 (AtCERK1) binding to chitopentaose (C05) and chitooctaose (C08).  FIG. 17A  shows AtCERK1 binding to chitopentaose (Chitin (C05)).  FIG. 17B  shows AtCERK1 binding to chitooctaose (Chitin (CO8)). For  FIGS. 17A-17B , seven 2-fold dilution series of analyte (1.56-100 μM) were used for each experiment; experimental binding curves are represented in solid lines, fitting curves in dashed lines; goodness of fit is described by the global fit R 2  on the mean value of each point; number of replicates performed using independent protein preparations (n) indicated; and kinetic parameters (k on  and k off ) are shown. 
     
    
    
     DETAILED DESCRIPTION 
     The following description sets forth exemplary methods, parameters, and the like. It should be recognized, however, that such description is not intended as a limitation on the scope of the present disclosure but is instead provided as a description of exemplary embodiments. 
     Genetically Altered Plants and Seeds 
     Certain aspects of the present disclosure relate to a genetically altered plant or plant part containing a nucleic acid sequence encoding a heterologous receptor polypeptide, wherein the heterologous receptor polypeptide is selected from the group of a first polypeptide with at least 70% sequence identity, at least 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or at least 99% sequence identity to SEQ ID NO:5 (i.e., chickpea,  Cicer arietinum  NFR5), a second polypeptide with at least 70% sequence identity, at least 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or at least 99% sequence identity to SEQ ID NO:7 (i.e., bean,  Phaseolus vulgaris  NFR5), a third polypeptide with at least 70% sequence identity, at least 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or at least 99% sequence identity to SEQ ID NO:9 (i.e., peanut,  Arachis  NFR5), a fourth polypeptide with at least 70% sequence identity, at least 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or at least 99% sequence identity to SEQ ID NO:11 (i.e.,  Lotus  LYS11), a fifth polypeptide with at least 70% sequence identity, at least 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or at least 99% sequence identity to SEQ ID NO:12 (i.e.,  Medicago  LYR1), a sixth polypeptide with at least 70% sequence identity, at least 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or at least 99% sequence identity to SEQ ID NO:13 (i.e.,  Parasponia  NFP1), a seventh polypeptide with at least 70% sequence identity, at least 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or at least 99% sequence identity to SEQ ID NO:16 (i.e., barley HvLysM-RLK1 (AK370300)), an eighth polypeptide with at least 70% sequence identity, at least 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or at least 99% sequence identity to SEQ ID NO:17 (i.e., barley HvLysM-RLK2 (AK357612)), a ninth polypeptide with at least 70% sequence identity, at least 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or at least 99% sequence identity to SEQ ID NO:18 (i.e., barley HvLysM-RLK3 AK372128), a tenth polypeptide with at least 70% sequence identity, at least 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or at least 99% sequence identity to SEQ ID NO:19 (i.e., barley HvLysM-RLK10 (HORVU4Hr1 G066170)), an eleventh polypeptide with at least 70% sequence identity, at least 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or at least 99% sequence identity to SEQ ID NO:20 (i.e., maize ZM1 (XP_020399958)), a twelfth polypeptide with at least 70% sequence identity, at least 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or at least 99% sequence identity to SEQ ID NO:21 (i.e., maize ZM5 (XP_008652982.1)), a thirteenth polypeptide with at least 70% sequence identity, at least 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or at least 99% sequence identity to SEQ ID NO:22 (i.e., apple NFP5 XP_008338966.1), or a fourteenth polypeptide with at least 70% sequence identity, at least 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or at least 99% sequence identity to SEQ ID NO:23 (i.e., strawberry NFR5 XP_004300586.2). In some embodiments, the heterologous receptor polypeptide is selected from the group of SEQ ID NO:5 (i.e., chickpea,  Cicer arietinum  NFR5), SEQ ID NO:7 (i.e., bean,  Phaseolus vulgaris  NFR5), SEQ ID NO:9 (i.e., peanut,  Arachis  NFR5), SEQ ID NO:11 (i.e.,  Lotus  LYS11), SEQ ID NO:12 (i.e.,  Medicago  LYR1), SEQ ID NO:13 (i.e.,  Parasponia  NFP1), SEQ ID NO:16 (i.e., barley HvLysM-RLK1 (AK370300)), SEQ ID NO:17 (i.e., barley HvLysM-RLK2 (AK357612)), SEQ ID NO:18 (i.e., barley HvLysM-RLK3 AK372128), SEQ ID NO:19 (i.e., barley HvLysM-RLK10 (HORVU4Hr1 G066170)), SEQ ID NO:20 (i.e., maize ZM1 (XP_020399958)), SEQ ID NO:21 (i.e., maize ZM5 (XP_008652982.1)), SEQ ID NO:22 (i.e., apple NFP5 XP_008338966.1), and SEQ ID NO:23 (i.e., strawberry NFR5 XP_004300586.2). In some embodiments, the expression of the heterologous receptor polypeptide allows the plant or part thereof to recognize lipo-chitooligosaccharides (LCOs) through the heterologous receptor polypeptide. In some embodiments, the LCOs are produced by nitrogen-fixing bacteria or by mycorrhizal fungi. In some embodiments, the LCOs are produced by nitrogen-fixing bacteria selected from the group of  Mesorhizobium loti, Mesorhizobium huakuii, Mesorhizobium mediterraneum, Mesorhizobium ciceri, Mesorhizobium  spp.,  Rhizobium mongolense, Rhizobium tropici, Rhizobium etli phaseoli, Rhizobium giardinii, Rhizobium leguminosarum  optionally  R. leguminosarum trifolii, R. leguminosarum viciae , and  R. leguminosarum phaseoli, Burkholderiales  optionally symbionts of  Mimosa, Sinorhizobium meliloti, Sinorhizobium medicae, Sinorhizobium fredii, Sinorhizobium fredii  NGR234,  Azorhizobium caulinodans, Bradyrhizobium japonicum, Bradyrhizobium elkanii, Bradyrhizobium liaonginense, Rhizobium  spp.,  Mesorhizobium  spp.,  Sinorhizobium  spp.,  Azorhizobium  spp.  Frankia  spp., or any combination thereof, or by mycorrhizal fungi selected from the group of  Acaulosporaceae  spp.,  Diversisporaceae  spp.,  Gigasporaceae  spp.,  Pacisporaceae  spp.,  Funneliformis  spp.,  Glomus  spp.,  Rhizophagus  spp.,  Sclerocystis  spp.,  Septoglomus  spp.,  Claroideoglomus  spp.,  Ambispora  spp.,  Archaeospora  spp.,  Geosiphon pyriformis, Paraglomus  spp., other species in the division  Glomeromycota , or any combination thereof. In some embodiments, the heterologous polypeptide is localized to a plant cell plasma membrane. In some embodiments, the plant cell is a root cell. In some embodiments, the root cell is a root epidermal cell or a root cortex cell. In some embodiments, the heterologous polypeptide is expressed in a developing plant root system. In some embodiments, the nucleic acid sequence is operably linked to a promoter. In some embodiments, the promoter is a root specific promoter. In some embodiments, the promoter is selected from the group of a NFR1 or NFR5/NFP promoter, the  Lotus  NFR5 promoter (SEQ ID NO: 24) and the  Lotus  NFR1 promoters (SEQ ID NO:25) the maize allothioneine promoter, the chitinase promoter, the maize ZRP2 promoter, the tomato LeExtl promoter, the glutamine synthetase soybean root promoter, the RCC3 promoter, the rice antiquitine promoter, the LRR receptor kinase promoter, or the  Arabidopsis  pCO2 promoter. In some embodiments, the promoter is a constitutive promoter optionally selected from the group of the CaMV35S promoter, a derivative of the CaMV35S promoter, the maize ubiquitin promoter, the trefoil promoter, a vein mosaic cassava virus promoter, or the  Arabidopsis  UBQ10 promoter. In some embodiments, the plant is selected from the group of corn (e.g., maize,  Zea mays ), rice (e.g.,  Oryza sativa, Oryza glaberrima, Zizania  spp.), barley (e.g.,  Hordeum vulgare ), wheat (e.g., common wheat, spelt, durum,  Triticum aestivum, Triticum spelta, Triticum durum, Triticum  spp.),  Trema  spp. (e.g.,  Trema cannabina, Trema cubense, Trema discolor, Trema domingensis, Trema integerrima, Trema lamarckiana, Trema micrantha, Trema orientalis, Trema philippinensis, Trema strigilosa, Trema tomentosa ), apple (e.g.,  Malus pumila ), pear (e.g.,  Pyrus communis, Pyrus xbretschneideri, Pyrus pyrifolia, Pyrus sinkiangensis, Pyrus pashia, Pyrus  spp.), plum (e.g., prune, damson, bullaces,  Prunus domestica, Prunus  salicina), apricot (e.g.,  Prunus armeniaca, Prunus brigantina, Prunus mandshurica, Prunus mume, Prunus sibirica ), peach (e.g., nectarine,  Prunus persica ), almond (e.g.,  Prunus dulcis, Prunus amygdalus ), walnut (e.g., Persian walnut, English walnut, black walnut,  Juglans regia, Juglans nigra, Juglans cinerea, Juglans californica ), strawberry (e.g.,  Fragaria×ananassa, Fragaria chiloensis, Fragaria virginiana, Fragaria vesca ), raspberry (e.g., European red raspberry, black raspberry,  Rubus idaeus, Rubus occidentalis, Rubus strigosus ), blackberry (e.g., evergreen blackberry, Himalayan blackberry,  Rubus fruticosus, Rubus ursinus, Rubus laciniatus, Rubus  argutus,  Rubus armeniacus, Rubus plicatus, Rubus ulmifolius, Rubus allegheniensis ), red currant (e.g.,  Ribes rubrum, Ribes spicatum, Ribesbes alpinum, Ribes schlechtendalii, Ribes multiflorum, Ribes petraeum, Ribes triste ), black currant (e.g.,  Ribes nigrum ), melon (e.g., watermelon, winter melon, casabas, cantaloupe, honeydew, muskmelon,  Citrullus lanatus, Benincasa hispida, Cucumis melo cantalupensis, Cucumis melo inodorus, Cucumis melo reticulatus ), cucumber (e.g., slicing cucumbers, pickling cucumbers, English cucumber,  Cucumis sativus ), pumpkin (e.g.,  Cucurbita pepo, Cucurbita maxima ), squash (e.g., gourd,  Cucurbita argyrosperma, Cucurbita ficifolia, Cucurbita maxima, Cucurbita moschata ), grape (e.g.,  Vitis vinifera, Vitis amurensis, Vitis labrusca, Vitis mustangensis, Vitis riparia, Vitis rotundifolia ), or hemp (e.g.,  cannabis, Cannabis sativa ). 
     In some embodiments of any of the above embodiments, the plant part is a leaf, a stem, a root, a root primordia, a flower, a seed, a fruit, a kernel, a grain, a cell, or a portion thereof. In some embodiments, the part is a fruit, a kernel, or a grain. 
     In some aspects, the present disclosure relates to a pollen grain or an ovule of the genetically altered plant of any of the above embodiments. 
     In some aspects, the present disclosure relates to a protoplast produced from the plant of any of the above embodiments. 
     In some aspects, the present disclosure relates to a tissue culture produced from protoplasts or cells from the plant of any of the above embodiments, wherein the cells or protoplasts are produced from a plant part selected from the group consisting of leaf, anther, pistil, stem, petiole, root, root primordia, root tip, fruit, seed, flower, cotyledon, hypocotyl, embryo, and meristematic cell. 
     In some aspects, the present disclosure relates to a genetically altered plant seed containing a nucleic acid sequence encoding a heterologous receptor polypeptide, wherein the heterologous receptor polypeptide is selected from the group of a first polypeptide with at least 70% sequence identity, at least 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or at least 99% sequence identity to SEQ ID NO:5 (i.e., chickpea,  Cicer arietinum  NFR5), a second polypeptide with at least 70% sequence identity, at least 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or at least 99% sequence identity to SEQ ID NO:7 (i.e., bean,  Phaseolus vulgaris  NFR5), a third polypeptide with at least 70% sequence identity, at least 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or at least 99% sequence identity to SEQ ID NO:9 (i.e., peanut,  Arachis  NFR5), a fourth polypeptide with at least 70% sequence identity, at least 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or at least 99% sequence identity to SEQ ID NO:11 (i.e.,  Lotus  LYS11), a fifth polypeptide with at least 70% sequence identity, at least 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or at least 99% sequence identity to SEQ ID NO:12 (i.e.,  Medicago  LYR1), a sixth polypeptide with at least 70% sequence identity, at least 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or at least 99% sequence identity to SEQ ID NO:13 (i.e.,  Parasponia  NFP1), a seventh polypeptide with at least 70% sequence identity, at least 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or at least 99% sequence identity to SEQ ID NO:16 (i.e., barley HvLysM-RLK1 (AK370300)), an eighth polypeptide with at least 70% sequence identity, at least 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or at least 99% sequence identity to SEQ ID NO:17 (i.e., barley HvLysM-RLK2 (AK357612)), a ninth polypeptide with at least 70% sequence identity, at least 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or at least 99% sequence identity to SEQ ID NO:18 (i.e., barley HvLysM-RLK3 AK372128), a tenth polypeptide with at least 70% sequence identity, at least 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or at least 99% sequence identity to SEQ ID NO:19 (i.e., barley HvLysM-RLK10 (HORVU4Hr1 G066170)), an eleventh polypeptide with at least 70% sequence identity, at least 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or at least 99% sequence identity to SEQ ID NO:20 (i.e., maize ZM1 (XP_020399958)), a twelfth polypeptide with at least 70% sequence identity, at least 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or at least 99% sequence identity to SEQ ID NO:21 (i.e., maize ZM5 (XP_008652982.1)), a thirteenth polypeptide with at least 70% sequence identity, at least 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or at least 99% sequence identity to SEQ ID NO:22 (i.e., apple NFP5 XP_008338966.1), or a fourteenth polypeptide with at least 70% sequence identity, at least 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or at least 99% sequence identity to SEQ ID NO:23 (i.e., strawberry NFR5 XP_004300586.2). In some embodiments, the heterologous receptor polypeptide is selected from the group of SEQ ID NO:5 (i.e., chickpea,  Cicer arietinum  NFR5), SEQ ID NO:7 (i.e., bean,  Phaseolus vulgaris  NFR5), SEQ ID NO:9 (i.e., peanut,  Arachis  NFR5), SEQ ID NO:11 (i.e.,  Lotus  LYS11), SEQ ID NO:12 (i.e.,  Medicago  LYR1), SEQ ID NO:13 (i.e.,  Parasponia  NFP1), SEQ ID NO:16 (i.e., barley HvLysM-RLK1 (AK370300)), SEQ ID NO:17 (i.e., barley HvLysM-RLK2 (AK357612)), SEQ ID NO:18 (i.e., barley HvLysM-RLK3 AK372128), SEQ ID NO:19 (i.e., barley HvLysM-RLK10 (HORVU4Hr1G066170)), SEQ ID NO:20 (i.e., maize ZM1 (XP_020399958)), SEQ ID NO:21 (i.e., maize ZM5 (XP_008652982.1)), SEQ ID NO:22 (i.e., apple NFP5 XP_008338966.1), and SEQ ID NO:23 (i.e., strawberry NFR5 XP_004300586.2). In some embodiments, the expression of the heterologous receptor polypeptide allows the plant or part thereof to recognize lipo-chitooligosaccharides (LCOs) through the heterologous receptor polypeptide. In some embodiments, the LCOs are produced by nitrogen-fixing bacteria or by mycorrhizal fungi. In some embodiments, the LCOs are produced by nitrogen-fixing bacteria selected from the group of  Mesorhizobium loti, Mesorhizobium huakuii, Mesorhizobium mediterraneum, Mesorhizobium ciceri, Mesorhizobium  spp.,  Rhizobium mongolense, Rhizobium tropici, Rhizobium etli phaseoli, Rhizobium giardinii, Rhizobium leguminosarum  optionally  R. leguminosarum trifolii, R. leguminosarum viciae , and  R. leguminosarum phaseoli, Burkholderiales  optionally symbionts of  Mimosa, Sinorhizobium meliloti, Sinorhizobium medicae, Sinorhizobium fredii, Sinorhizobium fredii  NGR234,  Azorhizobium caulinodans, Bradyrhizobium japonicum, Bradyrhizobium elkanii, Bradyrhizobium liaonginense, Rhizobium  spp.,  Mesorhizobium  spp.,  Sinorhizobium  spp.,  Azorhizobium  spp.  Frankia  spp., or any combination thereof, or by mycorrhizal fungi selected from the group of  Acaulosporaceae  spp.,  Diversisporaceae  spp.,  Gigasporaceae  spp.,  Pacisporaceae  spp.,  Funneliformis  spp.,  Glomus  spp.,  Rhizophagus  spp.,  Sclerocystis  spp.,  Septoglomus  spp.,  Claroideoglomus  spp.,  Ambispora  spp.,  Archaeospora  spp.,  Geosiphon pyriformis, Paraglomus  spp., other species in the division  Glomeromycota , or any combination thereof. In some embodiments, the heterologous polypeptide is localized to a plant cell plasma membrane when the seed is grown into a plant. In some embodiments, the plant cell is a root cell. In some embodiments, the root cell is a root epidermal cell or a root cortex cell. In some embodiments, the heterologous polypeptide is expressed in a developing plant root system when the seed is grown into a plant. In some embodiments, the nucleic acid sequence is operably linked to a promoter. In some embodiments, the promoter is a root specific promoter. In some embodiments, the promoter is selected from the group of a NFR1 or NFR5/NFP promoter, the  Lotus  NFR5 promoter (SEQ ID NO: 24) and the  Lotus  NFR1 promoters (SEQ ID NO:25) the maize allothioneine promoter, the chitinase promoter, the maize ZRP2 promoter, the tomato LeExtl promoter, the glutamine synthetase soybean root promoter, the RCC3 promoter, the rice antiquitine promoter, the LRR receptor kinase promoter, or the  Arabidopsis  pCO2 promoter. In some embodiments, the promoter is a constitutive promoter optionally selected from the group of the CaMV35S promoter, a derivative of the CaMV35S promoter, the maize ubiquitin promoter, the trefoil promoter, a vein mosaic cassava virus promoter, or the  Arabidopsis  UBQ10 promoter. In some embodiments, the plant is selected from the group of corn (e.g., maize,  Zea mays ), rice (e.g.,  Oryza sativa, Oryza glaberrima, Zizania  spp.), barley (e.g.,  Hordeum vulgare ), wheat (e.g., common wheat, spelt, durum,  Triticum aestivum, Triticum spelta, Triticum durum, Triticum  spp.),  Trema  spp. (e.g.,  Trema cannabina, Trema cubense, Trema discolor, Trema domingensis, Trema integerrima, Trema lamarckiana, Trema micrantha, Trema orientalis, Trema philippinensis, Trema strigilosa, Trema tomentosa ), apple (e.g.,  Malus pumila ), pear (e.g.,  Pyrus communis, Pyrus xbretschneideri, Pyrus pyrifolia, Pyrus sinkiangensis, Pyrus pashia, Pyrus  spp.), plum (e.g., prune, damson, bullaces,  Prunus domestica, Prunus salicina ), apricot (e.g.,  Prunus armeniaca, Prunus brigantina, Prunus mandshurica, Prunus mume, Prunus sibirica ), peach (e.g., nectarine,  Prunus persica ), almond (e.g.,  Prunus dulcis, Prunus amygdalus ), walnut (e.g., Persian walnut, English walnut, black walnut,  Juglans regia, Juglans nigra, Juglans cinerea, Juglans californica ), strawberry (e.g.,  Fragaria×ananassa, Fragaria chiloensis, Fragaria virginiana, Fragaria vesca ), raspberry (e.g., European red raspberry, black raspberry,  Rubus idaeus, Rubus occidentalis, Rubus strigosus ), blackberry (e.g., evergreen blackberry, Himalayan blackberry,  Rubus fruticosus, Rubus ursinus, Rubus laciniatus, Rubus argutus, Rubus armeniacus, Rubus plicatus, Rubus ulmifolius, Rubus allegheniensis ), red currant (e.g.,  Ribes rubrum, Ribes spicatum, Rib esbes alpinum, Ribes schlechtendalii, Ribes multiflorum, Ribes petraeum, Ribes triste ), black currant (e.g.,  Ribes nigrum ), melon (e.g., watermelon, winter melon, casabas, cantaloupe, honeydew, muskmelon,  Citrullus lanatus, Benincasa hispida, Cucumis melo cantalupensis, Cucumis melo inodorus, Cucumis melo reticulatus ), cucumber (e.g., slicing cucumbers, pickling cucumbers, English cucumber,  Cucumis sativus ), pumpkin (e.g.,  Cucurbita pepo, Cucurbita maxima ), squash (e.g., gourd,  Cucurbita argyrosperma, Cucurbita ficifolia, Cucurbita maxima, Cucurbita moschata ), grape (e.g.,  Vitis vinifera, Vitis amurensis, Vitis labrusca, Vitis mustangensis, Vitis riparia, Vitis rotundifolia ), or hemp (e.g.,  cannabis, Cannabis sativa ). 
     In some aspects, the present disclosure relates to a plant produced from the genetically altered plant seed of any one of the above embodiments, wherein the plant the plant expresses the heterologous polypeptide, and wherein the expression of the heterologous polypeptide allows the plant to recognize lipo-chitooligosaccharides (LCOs) through the heterologous receptor polypeptide. 
     In some aspects, the present disclosure related to a plant or part thereof able to recognize LCOs containing at least one modified nucleic acid sequence containing at least one coding sequence of a high affinity and/or high selectivity LCO receptor in the plant or part thereof, wherein the LCO receptor is expressed in the plant or part thereof; wherein the expression of the LCO receptor allows the plant to recognize LCOs. In some embodiments, the present disclosure related to a plant or part thereof able to recognize LCOs with high affinity and/or high selectivity containing at least one modified nucleic acid sequence containing at least one coding sequence of a high affinity and/or high selectivity LCO receptor in the plant or part thereof, wherein the high affinity and/or high selectivity LCO receptor is expressed in the plant or part thereof; wherein the expression of the high affinity and/or high selectivity LCO receptor allows the plant to recognize LCOs with high affinity and/or high selectivity. In some embodiments, the LCO receptor is from a legume. 
     LysM receptors are a well known and well understood type of receptor. LysM receptors have three characteristic domains located in the ectodomain of the protein: LysM1, LysM2, and LysM3, which are present in this order on the protein sequence. The LysM1 domain is located toward the N-terminal end of the protein sequence, and is preceded by an N-terminal signal peptide as well as a C(x)xxxC motif. The LysM1 domain is separated from the LysM2 domain by a CxC motif, and the LysM2 domain is separated from the LysM3 domain by a CxC motif as well. The three LysM motifs, as well as the C(x)xxxC and CxC motif are clearly shown in  FIGS. 8A-8C .  FIGS. 9A-9B ,  FIGS. 10A-10B , and  FIGS. 11A-11B  show individual alignments of Nod factor (e.g., LCO) LysM receptors, EPS LysM receptors, and chitin (CO) as well as PGN LysM receptors, again clearly depicting the three LysM motifs as well as the C(x)xxxC and CxC motifs. The category of LysM receptors is therefore known by one of skill in the art. 
     As used in the present disclosure, the term “selectivity” refers to the differentiation between different polysaccharide ligands, specifically between lipo-chitooligosaccharides (LCOs) as a class and other polysaccharide ligands, preferably chitooligosaccharides (COs). The LysM receptors of the present disclosure contain a hydrophobic patch in their LysM2 domain. This hydrophobic patch confers selective recognition of LCOs over COs, and therefore LysM receptors with the hydrophobic patch have high selectivity as compared to LysM receptors without the hydrophobic patch. 
     As used in the present disclosure, the term “affinity” refers to affinity for LCOs generally. Again, the hydrophobic patch present in the LysM2 domain of LysM receptors of the present disclosure confers higher affinity for LCOs. Therefore, LysM receptors with the hydrophobic patch have high affinity as compared to LysM receptors without the hydrophobic patch. Affinity can be measured using the methods described in the Examples below, and using other methods known in the art that measure binding kinetics, association, dissociation, and K D . For at least these reasons, the high affinity and high selectivity LysM receptors of the present disclosure will be readily understood by one of skill in the art. 
     Methods of Producing and Cultivating Genetically Altered Plants 
     Certain aspects of the present disclosure relate to a method of producing the genetically altered plant of any of the above embodiments, comprising introducing a genetic alteration to the plant comprising the nucleic acid sequence. In some embodiments, the nucleic acid sequence is operably linked to a promoter. In some embodiments, the promoter is a root specific promoter. In some embodiments, the promoter is selected from the group of a NFR1 or NFR5/NFP promoter, the  Lotus  NFR5 promoter (SEQ ID NO: 24) and the  Lotus  NFR1 promoters (SEQ ID NO:25) the maize allothioneine promoter, the chitinase promoter, the maize ZRP2 promoter, the tomato LeExtl promoter, the glutamine synthetase soybean root promoter, the RCC3 promoter, the rice antiquitine promoter, the LRR receptor kinase promoter, or the  Arabidopsis  pCO2 promoter. In some embodiments, the promoter is a constitutive promoter optionally selected from the group of the CaMV35S promoter, a derivative of the CaMV35S promoter, the maize ubiquitin promoter, the trefoil promoter, a vein mosaic cassava virus promoter, or the  Arabidopsis  UBQ10 promoter. In some embodiments, the nucleic acid sequence is inserted into the genome of the plant so that the nucleic acid sequence is operably linked to an endogenous promoter. In some embodiments, the endogenous promoter is a root specific promoter. 
     Certain aspects of the present disclosure relate to a method of producing a genetically altered plant able to recognize LCOs, comprising the steps of: introducing a genetic alteration to the plant comprising the provision of an ability for LCOs produced by nitrogen-fixing bacteria and/or mycorrhizal fungi to be recognized, thereby enabling the plant to recognize LCOs. 
     In some aspects, the present disclosure relates to a method of producing a genetically altered plant able to recognize LCOs, comprises the steps of: introducing a genetic alteration to the plant comprising the provision of an ability for LCOs produced by nitrogen-fixing bacteria and/or mycorrhizal fungi to be recognized with high affinity and/or high selectivity, thereby enabling the plant to recognize LCOs with high affinity and/or high selectivity. 
     In some aspects, the present disclosure relates to a method of cultivating a plant with the ability to recognize LCOs, comprising the steps of: providing a seed with one or more genetic alterations that provide an ability for LCOs produced by nitrogen-fixing bacteria and/or mycorrhizal fungi to be recognized, wherein the seed produces a plant with the ability to recognize LCOs produced by nitrogen-fixing bacteria and/or mycorrhizal fungi; cultivating the plant under conditions where the ability to recognize LCOs produced by nitrogen-fixing bacteria and/or mycorrhizal fungi results in increased growth, yield, and/or biomass, as compared to a plant grown under the same conditions that lacks the one or more genetic alterations. In some embodiments, the plant is cultivated in nutrient-poor soil. 
     In some aspects, the present disclosure relates to a method of cultivating a plant with the ability to recognize LCOs with high affinity and/or high selectivity, comprising the steps of: providing a seed with one or more genetic alterations that provide an ability for LCOs produced by nitrogen-fixing bacteria and/or mycorrhizal fungi to be recognized with high affinity and/or high selectivity, wherein the seed produces a plant with the ability to recognize LCOs produced by nitrogen-fixing bacteria and/or mycorrhizal fungi with high affinity and/or high selectivity; cultivating the plant under conditions where the ability to recognize LCOs produced by nitrogen-fixing bacteria and/or mycorrhizal fungi with high affinity and/or high selectivity results in increased growth, yield, and/or biomass, as compared to a plant grown under the same conditions that lacks the one or more genetic alterations. In some embodiments, the plant is cultivated in nutrient-poor soil. 
     In some aspects, the present disclosure relates to a method of cultivating a plant with the ability to recognize LCOs, comprising the steps of: providing a tissue culture or protoplast with one or more genetic alterations that provide an ability for LCOs produced by nitrogen-fixing bacteria and/or mycorrhizal fungi to be recognized; regenerating the tissue culture or protoplast into a plantlet; growing the plantlet into a plant, wherein the plant has the ability to recognize LCOs produced by nitrogen-fixing bacteria and/or mycorrhizal fungi; transplanting the plant into conditions where the ability to recognize LCOs produced by nitrogen-fixing bacteria and/or mycorrhizal fungi results in increased growth, yield, and/or biomass, as compared to a plant grown under the same conditions that lacks the one or more genetic alterations. In some embodiments, the plant is cultivated in nutrient-poor soil. 
     In some aspects, the present disclosure relates to a method of cultivating a plant with the ability to recognize LCOs with high affinity and/or high selectivity, comprising the steps of: providing a tissue culture or protoplast with one or more genetic alterations that provide an ability for LCOs produced by nitrogen-fixing bacteria and/or mycorrhizal fungi to be recognized with high affinity and/or high selectivity, regenerating the tissue culture or protoplast into a plantlet; growing the plantlet into a plant, wherein the plant has the ability to recognize LCOs produced by produced by nitrogen-fixing bacteria and/or mycorrhizal fungi with high affinity and/or high selectivity; transplanting the plant into conditions where the ability to recognize LCOs produced by nitrogen-fixing bacteria and/or mycorrhizal fungi with high affinity and/or high selectivity results in increased growth, yield, and/or biomass, as compared to a plant grown under the same conditions that lacks the one or more genetic alterations. In some embodiments, the plant is cultivated in nutrient-poor soil. 
     In some embodiments of any of the above methods, the ability to recognize LCOs is conferred by a nucleic acid sequence encoding a heterologous receptor polypeptide, wherein the heterologous receptor polypeptide is selected from the group of a first polypeptide with at least 70% sequence identity, at least 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or at least 99% sequence identity to SEQ ID NO:5 (i.e., chickpea,  Cicer arietinum  NFR5), a second polypeptide with at least 70% sequence identity, at least 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or at least 99% sequence identity to SEQ ID NO:7 (i.e., bean,  Phaseolus vulgaris  NFR5), a third polypeptide with at least 70% sequence identity, at least 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or at least 99% sequence identity to SEQ ID NO:9 (i.e., peanut,  Arachis  NFR5), a fourth polypeptide with at least 70% sequence identity, at least 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or at least 99% sequence identity to SEQ ID NO:11 (i.e.,  Lotus  LYS11), a fifth polypeptide with at least 70% sequence identity, at least 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or at least 99% sequence identity to SEQ ID NO:12 (i.e.,  Medicago  LYR1), a sixth polypeptide with at least 70% sequence identity, at least 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or at least 99% sequence identity to SEQ ID NO:13 (i.e.,  Parasponia  NFP1), a seventh polypeptide with at least 70% sequence identity, at least 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or at least 99% sequence identity to SEQ ID NO:16 (i.e., barley HvLysM-RLK1 (AK370300)), an eighth polypeptide with at least 70% sequence identity, at least 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or at least 99% sequence identity to SEQ ID NO:17 (i.e., barley HvLysM-RLK2 (AK357612)), a ninth polypeptide with at least 70% sequence identity, at least 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or at least 99% sequence identity to SEQ ID NO:18 (i.e., barley HvLysM-RLK3 AK372128), a tenth polypeptide with at least 70% sequence identity, at least 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or at least 99% sequence identity to SEQ ID NO:19 (i.e., barley HvLysM-RLK10 (HORVU4Hr1 G066170)), an eleventh polypeptide with at least 70% sequence identity, at least 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or at least 99% sequence identity to SEQ ID NO:20 (i.e., maize ZM1 (XP_020399958)), a twelfth polypeptide with at least 70% sequence identity, at least 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or at least 99% sequence identity to SEQ ID NO:21 (i.e., maize ZM5 (XP_008652982.1)), a thirteenth polypeptide with at least 70% sequence identity, at least 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or at least 99% sequence identity to SEQ ID NO:22 (i.e., apple NFP5 XP_008338966.1), or a fourteenth polypeptide with at least 70% sequence identity, at least 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or at least 99% sequence identity to SEQ ID NO:23 (i.e., strawberry NFR5 XP_004300586.2). In some embodiments, the heterologous receptor polypeptide is selected from the group of SEQ ID NO:5 (i.e., chickpea,  Cicer arietinum  NFR5), SEQ ID NO:7 (i.e., bean,  Phaseolus vulgaris  NFR5), SEQ ID NO:9 (i.e., peanut,  Arachis  NFR5), SEQ ID NO:11 (i.e.,  Lotus  LYS11), SEQ ID NO:12 (i.e.,  Medicago  LYR1), SEQ ID NO:13 (i.e.,  Parasponia  NFP1), SEQ ID NO:16 (i.e., barley HvLysM-RLK1 (AK370300)), SEQ ID NO:17 (i.e., barley HvLysM-RLK2 (AK357612)), SEQ ID NO:18 (i.e., barley HvLysM-RLK3 AK372128), SEQ ID NO:19 (i.e., barley HvLysM-RLK10 (HORVU4Hr1 G066170)), SEQ ID NO:20 (i.e., maize ZM1 (XP_020399958)), SEQ ID NO:21 (i.e., maize ZM5 (XP_008652982.1)), SEQ ID NO:22 (i.e., apple NFP5 XP_008338966.1), and SEQ ID NO:23 (i.e., strawberry NFR5 XP_004300586.2). In some embodiments, the expression of the heterologous receptor polypeptide allows the plant or part thereof to recognize lipo-chitooligosaccharides (LCOs) through the heterologous receptor polypeptide. In some embodiments, the LCOs are produced by nitrogen-fixing bacteria or by mycorrhizal fungi. In some embodiments, the LCOs are produced by nitrogen-fixing bacteria selected from the group of  Mesorhizobium loti, Mesorhizobium huakuii, Mesorhizobium mediterraneum, Mesorhizobium ciceri, Mesorhizobium  spp.,  Rhizobium mongolense, Rhizobium tropici, Rhizobium etli phaseoli, Rhizobium giardinii, Rhizobium leguminosarum  optionally  R. leguminosarum trifolii, R. leguminosarum viciae , and  R. leguminosarum phaseoli, Burkholderiales  optionally symbionts of  Mimosa, Sinorhizobium meliloti, Sinorhizobium medicae, Sinorhizobium fredii, Sinorhizobium fredii  NGR234,  Azorhizobium caulinodans, Bradyrhizobium japonicum, Bradyrhizobium elkanii, Bradyrhizobium liaonginense, Rhizobium  spp.,  Mesorhizobium  spp.,  Sinorhizobium  spp.,  Azorhizobium  spp.  Frankia  spp., or any combination thereof, or by mycorrhizal fungi selected from the group of  Acaulosporaceae  spp.,  Diversisporaceae  spp.,  Gigasporaceae  spp.,  Pacisporaceae  spp.,  Funneliformis  spp.,  Glomus  spp.,  Rhizophagus  spp.,  Sclerocystis  spp.,  Septoglomus  spp.,  Claroideoglomus  spp.,  Ambispora  spp.,  Archaeospora  spp.,  Geosiphon pyriformis, Paraglomus  spp., other species in the division  Glomeromycota , or any combination thereof. In some embodiments, the heterologous polypeptide is localized to a plant cell plasma membrane. In some embodiments, the plant cell is a root cell. In some embodiments, the root cell is a root epidermal cell or a root cortex cell. In some embodiments, the heterologous polypeptide is expressed in a developing plant root system. In some embodiments, the nucleic acid sequence is operably linked to a promoter. In some embodiments, the promoter is a root specific promoter. In some embodiments, the promoter is selected from the group of a NFR1 or NFR5/NFP promoter, the  Lotus  NFR5 promoter (SEQ ID NO: 24) and the  Lotus  NFR1 promoters (SEQ ID NO:25) the maize allothioneine promoter, the chitinase promoter, the maize ZRP2 promoter, the tomato LeExtl promoter, the glutamine synthetase soybean root promoter, the RCC3 promoter, the rice antiquitine promoter, the LRR receptor kinase promoter, or the  Arabidopsis  pCO2 promoter. In some embodiments, the promoter is a constitutive promoter optionally selected from the group of the CaMV35S promoter, a derivative of the CaMV35S promoter, the maize ubiquitin promoter, the trefoil promoter, a vein mosaic cassava virus promoter, or the  Arabidopsis  UBQ10 promoter. In some embodiments, the plant is selected from the group of corn (e.g., maize,  Zea mays ), rice (e.g.,  Oryza sativa, Oryza glaberrima, Zizania  spp.), barley (e.g.,  Hordeum vulgare ), wheat (e.g., common wheat, spelt, durum,  Triticum aestivum, Triticum spelta, Triticum durum, Triticum  spp.),  Trema  spp. (e.g.,  Trema cannabina, Trema cubense, Trema discolor, Trema domingensis, Trema integerrima, Trema lamarckiana, Trema micrantha, Trema orientalis, Trema philippinensis, Trema strigilosa, Trema tomentosa ), apple (e.g.,  Malus pumila ), pear (e.g.,  Pyrus communis, Pyrus xbretschneideri, Pyrus pyrifolia, Pyrus sinkiangensis, Pyrus pashia, Pyrus  spp.), plum (e.g., prune, damson, bullaces,  Prunus domestica, Prunus salicina ), apricot (e.g.,  Prunus armeniaca, Prunus brigantina, Prunus mandshurica, Prunus mume, Prunus sibirica ), peach (e.g., nectarine,  Prunus persica ), almond (e.g.,  Prunus dulcis, Prunus amygdalus ), walnut (e.g., Persian walnut, English walnut, black walnut,  Juglans regia, Juglans nigra, Juglans cinerea, Juglans californica ), strawberry (e.g.,  Fragaria×ananassa, Fragaria chiloensis, Fragaria virginiana, Fragaria vesca ), raspberry (e.g., European red raspberry, black raspberry,  Rubus idaeus, Rubus occidentalis, Rubus strigosus ), blackberry (e.g., evergreen blackberry, Himalayan blackberry,  Rubus fruticosus, Rubus ursinus, Rubus laciniatus, Rubus argutus, Rubus armeniacus, Rubus plicatus, Rubus ulmifolius, Rubus allegheniensis ), red currant (e.g.,  Ribes rubrum, Ribes spicatum, Ribesbes alpinum, Ribes schlechtendalii, Ribes multiflorum, Ribes petraeum, Ribes triste ), black currant (e.g.,  Ribes nigrum ), melon (e.g., watermelon, winter melon, casabas, cantaloupe, honeydew, muskmelon,  Citrullus lanatus, Benincasa hispida, Cucumis melo cantalupensis, Cucumis melo inodorus, Cucumis melo reticulatus ), cucumber (e.g., slicing cucumbers, pickling cucumbers, English cucumber,  Cucumis sativus ), pumpkin (e.g.,  Cucurbita pepo, Cucurbita maxima ), squash (e.g., gourd,  Cucurbita argyrosperma, Cucurbita ficifolia, Cucurbita maxima, Cucurbita moschata ), grape (e.g.,  Vitis vinifera, Vitis amurensis, Vitis labrusca, Vitis mustangensis, Vitis riparia, Vitis rotundifolia ), or hemp (e.g.,  cannabis, Cannabis sativa ). 
     Molecular Biological Methods to Produce Genetically Altered Plants and Plant Cells 
     One embodiment of the present invention provides a genetically altered plant or plant cell comprising one or more modified plant genes and/or introduced genes. For example, the present disclosure provides genetically altered plants with a nucleic acid sequence encoding a heterologous receptor polypeptide. The heterologous receptor allows the plants to recognize lipo-chitooligosaccharides (LCOs) through the heterologous receptor polypeptide. 
     Transformation and generation of genetically altered monocotyledonous and dicotyledonous plant cells is well known in the art. See, e.g., Weising, et al., Ann. Rev. Genet. 22:421-477 (1988); U.S. Pat. No. 5,679,558;  Agrobacterium  Protocols, ed: Gartland, Humana Press Inc. (1995); and Wang, et al. Acta Hort. 461:401-408 (1998). The choice of method varies with the type of plant to be transformed, the particular application and/or the desired result. The appropriate transformation technique is readily chosen by the skilled practitioner. 
     Any methodology known in the art to delete, insert or otherwise modify the cellular DNA (e.g., genomic DNA and organelle DNA) can be used in practicing the inventions disclosed herein. As an example, the CRISPR/Cas-9 and related systems may be used to insert a heterologous gene to a targeted site in the genomic DNA or substantially edit an endogenous gene to express the heterologous gene. For example, a disarmed Ti plasmid, containing a genetic construct for deletion or insertion of a target gene, in  Agrobacterium tumefaciens  can be used to transform a plant cell, and thereafter, a transformed plant can be regenerated from the transformed plant cell using procedures described in the art, for example, in EP 0116718, EP 0270822, PCT publication WO 84/02913 and published European Patent application (“EP”) 0242246. Ti-plasmid vectors each contain the gene between the border sequences, or at least located to the left of the right border sequence, of the T-DNA of the Ti-plasmid. Of course, other types of vectors can be used to transform the plant cell, using procedures such as direct gene transfer (as described, for example in EP 0233247), pollen mediated transformation (as described, for example in EP 0270356, PCT publication WO 85/01856, and U.S. Pat. No. 4,684,611), plant RNA virus-mediated transformation (as described, for example in EP 0 067 553 and U.S. Pat. No. 4,407,956), liposome-mediated transformation (as described, for example in U.S. Pat. No. 4,536,475), and other methods such as the methods for transforming certain lines of corn (e.g., U.S. Pat. No. 6,140,553; Fromm et al., Bio/Technology (1990) 8, 833 839); Gordon-Kamm et al., The Plant Cell, (1990) 2, 603 618) and rice (Shimamoto et al., Nature, (1989) 338, 274 276; Datta et al., Bio/Technology, (1990) 8, 736 740) and the method for transforming monocots generally (PCT publication WO 92/09696). For cotton transformation, the method described in PCT patent publication WO 00/71733 can be used. For soybean transformation, reference is made to methods known in the art, e.g., Hinchee et al. (Bio/Technology, (1988) 6, 915) and Christou et al. (Trends Biotech, (1990) 8, 145) or the method of WO 00/42207. 
     Genetically altered plants of the present invention can be used in a conventional plant breeding scheme to produce more genetically altered plants with the same characteristics, or to introduce the genetic alteration(s) in other varieties of the same or related plant species. Seeds, which are obtained from the altered plants, preferably contain the genetic alteration(s) as a stable insert in chromosomal or organelle DNA or as modifications to an endogenous gene or promoter. Plants comprising the genetic alteration(s) in accordance with the invention include plants comprising, or derived from, root stocks of plants comprising the genetic alteration(s) of the invention, e.g., fruit trees or ornamental plants. Hence, any non-transgenic grafted plant parts inserted on a transformed plant or plant part are included in the invention. 
     Introduced genetic elements, whether in an expression vector or expression cassette, which result in the expression of an introduced gene will typically utilize a plant-expressible promoter. A ‘plant-expressible promoter’ as used herein refers to a promoter that ensures expression of the genetic alteration(s) of the invention in a plant cell. Examples of promoters directing constitutive expression in plants are known in the art and include: the strong constitutive 35S promoters (the “35S promoters”) of the cauliflower mosaic virus (CaMV), e.g., of isolates CM 1841 (Gardner et al., Nucleic Acids Res, (1981) 9, 2871 2887), CabbB S (Franck et al., Cell (1980) 21, 285 294) and CabbB JI (Hull and Howell, Virology, (1987) 86, 482 493); promoters from the ubiquitin family (e.g., the maize ubiquitin promoter of Christensen et al., Plant Mol Biol, (1992) 18, 675-689), the gos2 promoter (de Pater et al., The Plant J (1992) 2, 834-844), the emu promoter (Last et al., Theor Appl Genet, (1990) 81, 581-588), actin promoters such as the promoter described by An et al. (The Plant J, (1996) 10, 107), the rice actin promoter described by Zhang et al. (The Plant Cell, (1991) 3, 1155-1165); promoters of the Cassava vein mosaic virus (WO 97/48819, Verdaguer et al. (Plant Mol Biol, (1998) 37, 1055-1067), the pPLEX series of promoters from Subterranean Clover Stunt Virus (WO 96/06932, particularly the S4 or S7 promoter), an alcohol dehydrogenase promoter, e.g., pAdh1S (GenBank accession numbers X04049, X00581), and the TR1′ promoter and the TR2′ promoter (the “TR1′ promoter” and “TR2′ promoter”, respectively) which drive the expression of the 1′ and 2′ genes, respectively, of the T DNA (Velten et al., EMBO J, (1984) 3, 2723 2730). 
     Alternatively, a plant-expressible promoter can be a tissue-specific promoter, e.g., a promoter directing a higher level of expression in some cells or tissues of the plant, e.g., in root epidermal cells. Examples of constitutive promoters that are often used in plant cells are the cauliflower mosaic (CaMV) 35S promoter (KAY et al. Science, 236, 4805, 1987), and various derivatives of the promoter, the maize ubiquitin promoter (CHRISTENSEN &amp; QUAIL, Transgenic Res, 5, 213-8, 1996), the trefoil promoter (Ljubql, MAEKAWA et al. Mol Plant Microbe Interact. 21, 375-82, 2008), the vein mosaic cassava virus promoter (International Application WO 97/48819), and the  Arabidopsis  UBQ10 promoter, Norris et al. Plant Mol. Biol. 21, 895-906, 1993). 
     In preferred embodiments, root specific promoters will be used. Non-limiting examples include a NFR1 or NFR5/NFP promoter, particularly the  Lotus  NFR5 promoter (SEQ ID NO: 24) and the  Lotus  NFR1 promoters (SEQ ID NO: 25) the maize allothioneine promoter (DE FRAMOND et al, FEBS 290, 103-106, 1991 Application EP 452269), the chitinase promoter (SAMAC et al. Plant Physiol 93, 907-914, 1990), the maize ZRP2 promoter (U.S. Pat. No. 5,633,363), the tomato LeExtlpromoter (Bucher et al. Plant Physiol. 128, 911-923, 2002), the glutamine synthetase soybean root promoter (HIREL et al. Plant Mol. Biol. 20, 207-218, 1992), the RCC3 promoter (PCT Application WO 2009/016104), the rice antiquitine promoter (PCT Application WO 2007/076115), the LRR receptor kinase promoter (PCT application WO 02/46439), and the  Arabidopsis  pCO2 promoter (HEIDSTRA et al, Genes Dev. 18, 1964-1969, 2004). These plant promoters can be combined with enhancer elements, they can be combined with minimal promoter elements, or can comprise repeated elements to ensure the expression profile desired. 
     In some embodiments, genetic elements to increase expression in plant cells can be utilized. For example, an intron at the 5′ end or 3′ end of an introduced gene, or in the coding sequence of the introduced gene, e.g., the hsp70 intron. Other such genetic elements can include, but are not limited to, promoter enhancer elements, duplicated or triplicated promoter regions, 5′ leader sequences different from another transgene or different from an endogenous (plant host) gene leader sequence, 3′ trailer sequences different from another transgene used in the same plant or different from an endogenous (plant host) trailer sequence. 
     An introduced gene of the present invention can be inserted in host cell DNA so that the inserted gene part is upstream (i.e., 5′) of suitable 3′ end transcription regulation signals (e.g., transcript formation and polyadenylation signals). This is preferably accomplished by inserting the gene in the plant cell genome (nuclear or chloroplast). Preferred polyadenylation and transcript formation signals include those of the nopaline synthase gene (Depicker et al., J. Molec Appl Gen, (1982) 1, 561-573), the octopine synthase gene (Gielen et al., EMBO J, (1984) 3:835 845), the SCSV or the Malic enzyme terminators (Schunmann et al., Plant Funct Biol, (2003) 30:453-460), and the T DNA gene 7 (Velten and Schell, Nucleic Acids Res, (1985) 13, 6981 6998), which act as 3′ untranslated DNA sequences in transformed plant cells. In some embodiments, one or more of the introduced genes are stably integrated into the nuclear genome. Stable integration is present when the nucleic acid sequence remains integrated into the nuclear genome and continues to be expressed (e.g., detectable mRNA transcript or protein is produced) throughout subsequent plant generations. Stable integration into and/or editing of the nuclear genome can be accomplished by any known method in the art (e.g., microparticle bombardment,  Agrobacterium -mediated transformation, CRISPR/Cas9, electroporation of protoplasts, microinjection, etc.). 
     The term recombinant or modified nucleic acids refers to polynucleotides which are made by the combination of two otherwise separated segments of sequence accomplished by the artificial manipulation of isolated segments of polynucleotides by genetic engineering techniques or by chemical synthesis. In so doing one may join together polynucleotide segments of desired functions to generate a desired combination of functions. 
     As used herein, the terms “overexpression” and “upregulation” refer to increased expression (e.g., of mRNA, polypeptides, etc.) relative to expression in a wild type organism (e.g., plant) as a result of genetic modification. In some embodiments, the increase in expression is a slight increase of about 10% more than expression in wild type. In some embodiments, the increase in expression is an increase of 50% or more (e.g., 60%, 70%, 80%, 100%, etc.) relative to expression in wild type. In some embodiments, an endogenous gene is overexpressed. In some embodiments, an exogenous gene is overexpressed by virtue of being expressed. Overexpression of a gene in plants can be achieved through any known method in the art, including but not limited to, the use of constitutive promoters, inducible promoters, high expression promoters (e.g., PsaD promoter), enhancers, transcriptional and/or translational regulatory sequences, codon optimization, modified transcription factors, and/or mutant or modified genes that control expression of the gene to be overexpressed. 
     Where a recombinant nucleic acid is intended for expression, cloning, or replication of a particular sequence, DNA constructs prepared for introduction into a host cell will typically comprise a replication system (e.g. vector) recognized by the host, including the intended DNA fragment encoding a desired polypeptide, and can also include transcription and translational initiation regulatory sequences operably linked to the polypeptide-encoding segment. Additionally, such constructs can include cellular localization signals (e.g., plasma membrane localization signals). In preferred embodiments, such DNA constructs are introduced into a host cell&#39;s genomic DNA, chloroplast DNA or mitochondrial DNA. 
     In some embodiments, a non-integrated expression system can be used to induce expression of one or more introduced genes. Expression systems (expression vectors) can include, for example, an origin of replication or autonomously replicating sequence (ARS) and expression control sequences, a promoter, an enhancer and necessary processing information sites, such as ribosome-binding sites, RNA splice sites, polyadenylation sites, transcriptional terminator sequences, and mRNA stabilizing sequences. Signal peptides can also be included where appropriate from secreted polypeptides of the same or related species, which allow the protein to cross and/or lodge in cell membranes, cell wall, or be secreted from the cell. 
     Selectable markers useful in practicing the methodologies of the invention disclosed herein can be positive selectable markers. Typically, positive selection refers to the case in which a genetically altered cell can survive in the presence of a toxic substance only if the recombinant polynucleotide of interest is present within the cell. Negative selectable markers and screenable markers are also well known in the art and are contemplated by the present invention. One of skill in the art will recognize that any relevant markers available can be utilized in practicing the inventions disclosed herein. 
     Screening and molecular analysis of recombinant strains of the present invention can be performed utilizing nucleic acid hybridization techniques. Hybridization procedures are useful for identifying polynucleotides, such as those modified using the techniques described herein, with sufficient homology to the subject regulatory sequences to be useful as taught herein. The particular hybridization techniques are not essential to the subject invention. As improvements are made in hybridization techniques, they can be readily applied by one of skill in the art. Hybridization probes can be labeled with any appropriate label known to those of skill in the art. Hybridization conditions and washing conditions, for example temperature and salt concentration, can be altered to change the stringency of the detection threshold. See, e.g., Sambrook et al. (1989) vide infra or Ausubel et al. (1995) Current Protocols in Molecular Biology, John Wiley &amp; Sons, NY, N.Y., for further guidance on hybridization conditions. 
     Additionally, screening and molecular analysis of genetically altered strains, as well as creation of desired isolated nucleic acids can be performed using Polymerase Chain Reaction (PCR). PCR is a repetitive, enzymatic, primed synthesis of a nucleic acid sequence. This procedure is well known and commonly used by those skilled in this art (see Mullis, U.S. Pat. Nos. 4,683,195, 4,683,202, and 4,800,159; Saiki et al. (1985) Science 230:1350-1354). PCR is based on the enzymatic amplification of a DNA fragment of interest that is flanked by two oligonucleotide primers that hybridize to opposite strands of the target sequence. The primers are oriented with the 3′ ends pointing towards each other. Repeated cycles of heat denaturation of the template, annealing of the primers to their complementary sequences, and extension of the annealed primers with a DNA polymerase result in the amplification of the segment defined by the 5′ ends of the PCR primers. Because the extension product of each primer can serve as a template for the other primer, each cycle essentially doubles the amount of DNA template produced in the previous cycle. This results in the exponential accumulation of the specific target fragment, up to several million-fold in a few hours. By using a thermostable DNA polymerase such as the Taq polymerase, which is isolated from the thermophilic bacterium  Thermus aquaticus , the amplification process can be completely automated. Other enzymes which can be used are known to those skilled in the art. 
     Nucleic acids and proteins of the present invention can also encompass homologues of the specifically disclosed sequences. Homology (e.g., sequence identity) can be 50%-100%. In some instances, such homology is greater than 80%, greater than 85%, greater than 90%, or greater than 95%. The degree of homology or identity needed for any intended use of the sequence(s) is readily identified by one of skill in the art. As used herein percent sequence identity of two nucleic acids is determined using an algorithm known in the art, such as that disclosed by Karlin and Altschul (1990) Proc. Natl. Acad. Sci. USA 87:2264-2268, modified as in Karlin and Altschul (1993) Proc. Natl. Acad. Sci. USA 90:5873-5877. Such an algorithm is incorporated into the NBLAST and XBLAST programs of Altschul et al. (1990) J. Mol. Biol. 215:402-410. BLAST nucleotide searches are performed with the NBLAST program, score=100, wordlength=12, to obtain nucleotide sequences with the desired percent sequence identity. To obtain gapped alignments for comparison purposes, Gapped BLAST is used as described in Altschul et al. (1997) Nucl. Acids. Res. 25:3389-3402. When utilizing BLAST and Gapped BLAST programs, the default parameters of the respective programs (NBLAST and XBLAST) are used. See www.ncbi.nih.gov. 
     Preferred host cells are plant cells. Recombinant host cells, in the present context, are those which have been genetically modified to contain an isolated nucleic molecule, contain one or more deleted or otherwise non-functional genes normally present and functional in the host cell, or contain one or more genes to produce at least one recombinant protein. The nucleic acid(s) encoding the protein(s) of the present invention can be introduced by any means known to the art which is appropriate for the particular type of cell, including without limitation, transformation, lipofection, electroporation or any other methodology known by those skilled in the art. 
     Having generally described this invention, the same will be better understood by reference to certain specific examples, which are included herein to further illustrate the invention and are not intended to limit the scope of the invention as defined by the claims. 
     EXAMPLES 
     The present disclosure is described in further detail in the following examples which are not in any way intended to limit the scope of the disclosure as claimed. The attached figures are meant to be considered as integral parts of the specification and description of the disclosure. The following examples are offered to illustrate, but not to limit the claimed disclosure. 
     Example 1: Expression and Purification of  Medicago  NFP Ectodomain 
     The following example describes the protein expression and purification materials and methods that were used to prepare protein for all of the following examples. 
     Materials and Methods 
     Expression and purification of  Medicago  NFP ectodomain: The  Medicago truncatula  NFP ectodomain (residues 28-246) was codon-optimized for insect cell expression (Genscript, Piscataway, USA) and cloned into the pOET4 baculovirus transfer vector (Oxford Expression Technologies). The native NFP signal peptide (residues 1-27, predicted by SignalP 4.1) was replaced with the AcMNPV gp67 signal peptide to facilitate secretion and a hexa-histidine tag was added to the C-terminus. Point mutants of NFP were engineered using site-directed mutagenesis. Recombinant baculoviruses were produced in Sf9 cells ( Spodoptera frugiperda ) using the FlashBac Gold kit (Oxford Expression technologies) according to the manufacturer&#39;s instructions with Lipofectin (ThermoFisher Scientific) as a transfection reagent. Protein expression was performed as follows. Suspension-cultured Sf9 cells were maintained with shaking at 299 K in serum-free MAX-XP (BD-Biosciences, discontinued) or HyClone SFX (GE Healthcare) medium supplemented with 1% Pen-Strep (10000 U/ml, Life technologies) and 1% CD lipid concentrate (Gibco). Protein expression was induced by adding recombinant passage 3 virus once the Sf9 cells reached a cell density of 1.0*10 7 {circumflex over ( )}6 cells/ml. After 5-7 days of expression, medium supernatant containing NFP ectodomains was harvested by centrifugation. This was followed by an overnight dialysis step against 50 mM Tris-HCl pH 8, 200 mM NaCl at 277 K. The NFP ectodomain was enriched by two subsequent steps of Ni-IMAC purification (HisTrap excel/HisTrap HP, both GE Healthcare). For crystallography experiments, N-glycans were removed using the endoglycosidase PNGase F (1:15 (w/w), room temperature, overnight). As a final purification step, NFP ectodomain was purified by SEC on a Superdex 200 10/300 or HiLoad Superdex 200 16/600 (both GE Healthcare) in phosphate buffered saline at pH 7.2 supplemented to a total of 500 mM NaCl (for binding assays) or 50 mM Tris-HCl, 200 mM NaCl (for crystallography). NFP ectodomain elutes as a single, homogeneous peak corresponding to a monomer. Point mutated versions of NFP were expressed and purified following the same protocol. 
     Example 2: Structural Characterization of  Medicago  NFP Ectodomain 
     The following example describes the structural characterization of the  Medicago  NFP protein ectodomain. 
     Materials and Methods 
     Crystallization and structure determination: Crystals of deglycosylated NFP ectodomain (see Example 1) were obtained using a vapour diffusion setup at 3-5 mg/ml in 0.2 M Na-acetate, 0.1 M Na-cacodylate pH 6.5, and 30% (w/v) PEG-8000. Crystals were cryoprotected in their crystallization condition by supplementing with 5% (w/v) PEG-400 before being snap-frozen in liquid nitrogen. Complete diffraction data to 2.85 Å resolution was obtained at the MaxLab 1911-3 beamline. The phase problem was solved by molecular replacement using Phaser from the PHENIX suite with a homology model based on the AtCERK1 ectodomain structure (PDB coordinates 4EBZ) as a search model. Model building and refinement was done using COOT and the PHENIX suite, respectively. The output pdb filled structural model was generated and its electrostatic surface potential was calculated using the PDB2PQR and APBS webservers (PMID: 21425296). The results were visualized in PyMol using APBS tools 2.1 (DeLano, W. L. (2002). PyMOL. DeLano Scientific, San Carlos, Calif., 700.). 
     Small-angle X-ray scattering (SAXS): Small-angle X-ray scattering of NFP-ECD was measured in batch at different concentrations (1, 2, 4 and 6 mg/ml for glycosylated NFP-ECD; and 1, 2 and 3 mg/ml for deglycosylated NFP-ECD and 1, 2, 4) in phosphate buffered saline, pH 7.4, 500 mM NaCl, at the EMBL β12 beamline PETRA III in a temperature-controlled cell at 20° C. at a wavelength of 1.24 Å. Data analysis and modelling was done using BioXTAS RAW, GNOM and the ATSAS program suite (Hopkins, J. B., Gillilan, R. E. &amp; Skou, S. BioXTAS RAW: Improvements to a free open-source program for small-angle X-ray scattering data reduction and analysis.  Journal of Applied Crystallography  50, 1545-1553 (2017); Svergun, D. I. Determination of the regularization parameter in indirect-transform methods using perceptual criteria.  Journal of Applied Crystallography  25, 495-503 (1992); Konarev, P. V., Volkov, V. V., Sokolova, A. V., Koch, M. H. J. &amp; Svergun, D. I. PRIMUS: a Windows PC-based system for small-angle scattering data analysis.  Journal of Applied Crystallography  36, 1277-1282 (2003)). The ab initio low resolution structure was modelled in DAMMIF using 15 individual reconstructions. Envelopes were aligned and averaged with DAMAVER (Franke, D. &amp; Svergun, D. I. DAMMIF, a program for rapid ab-initio shape determination in small-angle scattering.  Journal of Applied Crystallography  42, 342-346 (2009)). The average was finally refined in DAMMIN (Svergun, D. I. Restoring Low Resolution Structure of Biological Macromolecules from Solution Scattering Using Simulated Annealing.  Biophysical Journal  76, 2879-2886 (1999)). NFP-ECD models with added N- and C-terminal tails were rigid-body fitted into envelopes with colors (Wriggers, W. &amp; Chacon, P. Using Situs for the registration of protein structures with low resolution bead models from x-ray solution scattering.  Journal of Applied Crystallography  914 34, 773-776 (2001)). Theoretical scattering curves were calculated in CRYSOL online (Svergun, D., Barberato, C. &amp; Koch, M. H. J. CRYSOL—a Program to Evaluate X-ray Solution Scattering of Biological Macromolecules from Atomic Coordinates.  Journal of Applied Crystallography  28, 768-773 (1995)). Dimensionless Kratky plots were prepared in BioXTAS RAW (Hopkins, J. B., Gillilan, R. E. &amp; Skou, S. BioXTAS RAW: Improvements to a free open-source program for small-angle X-ray scattering data reduction and analysis.  Journal of Applied Crystallography  50, 1545-1553 (2017)). The molecular weight derived from the forward scattering was determined using an internal BSA standard. Mixtures were analysed with OLIGOMER (Konarev, P. V., Volkov, V. V., Sokolova, A. V., Koch, M. H. J. &amp; Svergun, D. I. PRIMUS: a Windows PC-based system for small-angle scattering data analysis.  Journal of Applied Crystallography  36, 1277-1282 (2003)). 
     Results 
     The structure of  Medicago  NFP-ECD was determined by molecular replacement using a homology model based on the inner low B-factor scaffold of AtCERK1. The complete structure of the NFP-ECD (residues 33-233) was built this way, including four N-glycosylations that were clearly resolved in the 2.8 Å electron density map. NFP forms a compact structure where three classical βααβ LysM domains are tightly interconnected and stabilized by 3 conserved disulfide bridges (C3-C104, C47-C166 and C102-C164) ( FIG. 1A ). The disulfide connectivity pattern and the overall scaffold arrangement is shared with other LysM-RLK proteins involved in chitin defense signaling, supporting a common evolutionary origin of these class of receptors (Zhang 2007). 
     To confirm the determined structure, small-angle X-ray scattering (SAXS) measurements were performed on the NFP-ECD.  FIG. 1B  shows the SAXS reconstructed envelope, which has the same overall dimensions as the determined structure and otherwise fits well with the crystal structure. In addition, an elongated ridged structure most likely originating from the C-terminal stalk region of the receptor was seen in the SAXS reconstructed envelope. This stalk region is conserved in length and to some degree in sequence amongst LCO LysM receptor homologues, suggesting that the ectodomain in these receptors needs a certain distance from the membrane for correct function. 
     SAXS measurements were also performed to compare deglycosylated and glycosylated NFP-ECD.  FIG. 14A  shows the SAXS analysis of deglycosylated NFP-ECD, while  FIG. 14B  shows the SAXS analysis of glycosylated NFP-ECD. The SAXS data and the reconstructed ab initio model are in agreement with the crystal structure, however in addition an elongated stem like structure is present ( FIG. 1B ). This stem region is most likely comprised of the C-terminal part of NFP which was not visible in the crystal structure and might serve to position the ectodomain of NFP at the correct distance from the plasma membrane.  FIG. 14C  compares the dimensionless Kratky plots for deglycosylated and glycosylated NFP-ECD, and this comparison showed that glycans have an effect on the globularity of NFP-ECD. Glycosylated NFP-ECD had a more globular shape, where the peak lay close to the Guinier-Kratky point (dotted line, left graph of  FIG. 14C ) and closer to the surface/volume ratio of an ideal sphere (0.82, dotted line, right graph of  FIG. 14C ). This more globular shape was likely due to the presence of 15-20 kDa of glycans. The loss of globularity and elongated shape became more pronounced and visible upon glycan removal (deglycosylated NFP-ECD in both graphs of  FIG. 14C ). 
     Example 3: NFP Binding Ability and Affinity for Different Chitooligosaccharide (CO), Lipochitooligosaccharide (LCO), and Carbohydrate Ligands 
     The following example describes experiments measuring NFP binding ability and affinity. These experiments were designed to investigate whether NFP has differential binding ability and affinity for different ligands. 
     Materials and Methods 
     Microscale thermophoresis (MST): NFP were fluorescently labelled (Protein Labeling Kit Blue NHS, NanoTemper Technologies). A constant concentration of NFP was used to measure binding to dilution series of ligands. The ligands used were CO4 chitin oligomer (corresponding to the backbone of  S. meliloti  LCO-IV), CO5 chitin oligomer (corresponding to the backbone of  S. meliloti  LCO-V), maltohexaose (carbohydrate from  S. meliloti ), and octosaccharide exopolysaccharide (EPS). Data analysis was performed in GraphPad Prism7 software (GraphPad Software, Inc.) using the sigmoidal dose-response model to obtain equilibrium dissociation constants values. 
     Biolayer interferometry (BLI): Binding of NFP and mutated versions of NFP to ligands was measured on an Octet RED 96 system (Pall ForteBio). The ligands used were LCO-IV (from  S. meliloti ), LCO-V (from  S. meliloti ), LCO-V (from  M. loti ), and C06 (from  M. loti ).  S. meliloti  LCO consists of a tetrameric/pentameric N-acetylglucosamine backbone that is 0-sulfated on the reducing terminal residue, 0-acetylated on the non-reducing terminal residue, and mono-N-acylated by unsaturated C16 acyl groups.  M. loti  LCO is a pentameric N-acetylglucosamine with a cis-vaccenic acid and a carbamoyl group at the non-reducing terminal residue together with a 2,4-O-acetylfucose at the reducing terminal residue. Biotinylated ligand conjugates were immobilized on streptavidin biosensors (kinetic quality, Pall ForteBio) at a concentration of 125-250 nM for 5 minutes. The binding assays using the  S. meliloti  ligands (LCO-IV and LCO-V) were replicated seven times, while the binding assays using the  M loti  ligands (LCO-V and C06) were replicated six times. Data analysis was performed in GraphPad Prism 6 software (GraphPad Software, Inc.). Equilibrium dissociation constants derived from the steady-state were determined by applying a non-linear regression (one site, specific binding) to the response at equilibrium plotted against the protein concentration. Kinetic parameters were determined by non-linear regression (association followed by dissociation) on the subtracted data. 
     Results 
     Since LCOs consist of a N-acetylglucosamine (chitin) backbone, the first tests measured whether NFP has affinity for CO4 and CO5 chitin oligomers that correspond to the backbone of  S. meliloti  LCO-IV and LCO-V, respectively. In microscale thermophoresis (MST) experiments, NFP was found to bind CO4 and CO5 with a dissociation constant of (Kd), 150 μM and 93 μM respectively. NFP is, however, not able to bind the unrelated carbohydrate ligands maltohexaose or octasaccharide exopolysaccharide purified from  S. meliloti . This shows that NFP selectively binds chitinous ligands. 
     LCO ligands are difficult to handle in solution due to the hydrophobic sticky nature and micelle phase, which hinder accurate concentration determination. To overcome this problem, previously developed chemistry to site-specifically label the reducing end of LCOs with a biotinylated linker was used. Using biolayer interferometry (BLI), it was found that NFP binds immobilized  S. meliloti  LCO-IV with a Kd of 26±0.2 μM and  S. meliloti  LCO-V with a Kd of 32±0.2 μM ( FIG. 2A ). Interestingly, NFP binding of  M. loti  LCO-V was not detected, and neither was NFP binding of  M. loti  C06 ( FIG. 2B ). 
     Further BLI assays showed that NFP-ECD bound  S. meliloti  LCO-V with an average K d  of 22.3±0.1 μM ( FIG. 15A ). NFP-ECD bound  M. loti  LCO-V weakly (Kd could not be fitted;  FIG. 15B ), and did not bind chitin ( FIG. 15C ). As shown in  FIGS. 15D-15E , elimination of the O-acetyl group on the non-reducing end in nodL-LCO-IV reduced binding to NFP-ECD by more than 10-fold (Kd of 133.2±0.3 μM) compared to wild type  S. meliloti  LCO-IV. Lack of the reducing end sulfate in nodH-LCO-IV drastically lowered binding to NFP-ECD by more than 21-fold (Kd of 275.3±1.3 μM), which could explain the reduced calcium spiking observed with this nonsulfated LCO in  Medicago  (Oldroyd, G. E. D., Mitra, R. M., Wais, R. J. &amp; Long, S. R. Evidence for structurally specific negative feedback in the Nod factor signal transduction pathway.  The Plant Journal  28, 191-284 199 (2001)). Similarly, both nodFE-LCO-IV containing vaccenic acid C18:1 instead of the C16:2 fatty acid and nodFL-LCO-IV lacking the acetyl group and displaying a C20:1 fatty acid showed no significant binding, reflecting the inability to induce both nodule development and infection thread formation after inoculation of the respective  S. meliloti  mutants (Ardourel, M. et al.  Rhizobium meliloti  lipooligosaccharide nodulation factors: different structural requirements for bacterial entry into target root hair cells and induction of plant symbiotic developmental responses.  Plant Cell  6, 1357-1374 (1994)). The data support the conclusion that NFP directly recognises all individual decorations present on its cognate LCO ligand, making NFP a highly specific receptor. 
     These results show that NFP has differential binding ability and affinity depending on the ligand. Moreover, these results show that NFP can differentiate between the same ligand produced by different symbiont species (compare results from  S. meliloti  LCO-V and  M. loti  LCO-V). This indicates that NFP can discriminate symbionts based on direct LCO binding. 
     Example 4: NFP Binding Ability and Affinity for Mutated Lipochitooligosaccharide (LCO) Ligands 
     Studies using bacterial mutants and measuring calcium transients in root hairs after LCO application have shown that side-chain decorations on the terminal N-acetylglucosamine residues are functionally important (Oldroyd GE1, Murray J D, Poole P S, and Downie J A.  Annu Rev Genet.  2011; 45:119-44). The following example describes experiments performed to understand how LCO side-chain decoration contributes to this apparent selectivity using NFP and its cognate LCO ligand from  S. meliloti.    
     Materials and Methods 
     Mutated lipochitooligosaccharide (LCO) ligands:  S. meliloti  LCO consists of a tetrameric/pentameric N-acetylglucosamine backbone that is O-sulfated on the reducing terminal residue, O-acetylated on the non-reducing terminal residue, and mono-N-acylated by unsaturated C16 acyl groups. The LCO ligands used here were purified from  S. meliloti  nodH, nodL, nodFE, and nodFL mutants. Each of these mutants lacks one or more of the side-chain decorations on the terminal moieties of LCO.  FIG. 3A  depicts  S. meliloti  LCO-IV, and indicates which side-chain decorations are altered in each mutant. 
     Ligand binding tests: Ligand binding tests were done as in Example 3. 
     Results 
       FIG. 3B  shows the results of ligand binding tests using mutated LCOs. Dramatically reduced binding to NFP was seen in tests with nodH-LCO, which has a missing sulfate modification, and in tests with nodL-LCO, which lacks an O-acetyl group. This is consistent with the perturbed nodulation and infection observed after plant inoculation with these  S. meliloti  mutants, as well as the decreased calcium transients found after applying these mutated LCOs. Similarly, tests using nodFE-LCO, which contains vaccenic acid C18:1 instead of the C16:2 fatty acid, reduced NFP binding. Further, the nodFL double mutant, which lacks an O-acetyl group and containing vaccenic acid C18:1, shows no binding to NFP. This reflects the perturbed nodulation, inability to induce nodule development, and lack of infection thread formation observed after plant inoculation with the respective  S. meliloti  mutants (Ardourel M, et al.  Plant Cell.  1994 October; 6(10):1357-74.). Taken together, this data shows that the NFP receptor can recognize individual modifications of its cognate LCO ligand. 
     Example 5: Identification of Important Residues for Lipochitooligosaccharide (LCO) Perception 
     The following example describes the use of a structurally-guided approach to identify important residues in NFP for LCO perception. After identifying important residues, NFP point mutations were created, and tested using the ligand-binding assays described above (see Example 3 and Example 4). 
     Materials and Methods 
     Structurally-guided residue identification: The NFP ectodomain was structurally aligned to ligand-bound CERK1. Then, the electrostatic surface potential was mapped to the previously-developed structure of the NFP ectodomain. The predicted ligand-binding location and electrostatic surface potential are depicted in  FIG. 4A . 
     Creation of NFP point mutations: The NFP leucine residues L147 and L154 were replaced with aspartate residues. Aspartate is similar in size to leucine, but negatively charged where leucine is hydrophobic. Point mutants of NFP were engineered using site-directed mutagenesis. In particular, a double-mutated NFP was engineered where the leucine residues L147 and L154 were replaced with aspartate residues to create the mutant NFP L147D L154D. Point mutated versions of NFP were expressed and purified as described in Example 1. 
     NFP mutant binding assays: The binding assay using NFP wild type (WT) protein was replicated seven times, while the binding assay using the NFP mutant NFP L147D L154D was replicated four times. 
     Biolayer interferometry (BLI): Binding of NFP WT and NFP L147D/L154D mutant to  S. meliloti  LCO-IV was measured on an Octet RED 96 system (Pall ForteBio).  S. meliloti  LCO consists of a tetrameric/pentameric N-acetylglucosamine backbone that is O-sulfated on the reducing terminal residue, 0-acetylated on the non-reducing terminal residue, and mono-N-acylated by unsaturated C16 acyl groups. Biotinylated ligand conjugates were immobilized on streptavidin biosensors (kinetic quality, Pall ForteBio) at a concentration of 125-250 nM for 5 minutes. The binding assays were replicated 7 times for the NFP WT, and 4 times for the NFP L147D/L154D mutant. Data analysis was performed in GraphPad Prism 6 software (GraphPad Software, Inc.). Equilibrium dissociation constants derived from the steady-state were determined by applying a non-linear regression (one site, specific binding) to the response at equilibrium plotted against the protein concentration. Kinetic parameters were determined by non-linear regression (association followed by dissociation) on the subtracted data. Results are shown in  FIGS. 16A-16C . Binding ofA.  thaliana  CERK1 (AtCERK1) to chitopentaose (C05) and chitooctaose (C08) was measured in the same way. Results are shown in  FIGS. 17A-17B . 
     Results 
       FIG. 4A  shows modelling of the NFP ectodomain bound to a ligand with predicted chitin and LCO fatty acid chain locations. Structural alignment of the NFP ectodomain with ligand-bound CERK1 positions chitin in the LysM2 binding groove of NFP without any obvious clashes. Strikingly, the electrostatic surface potential revealed a hydrophobic patch on the NFP ectodomain that is located near the non-reducing moiety of the docked chitin molecule, which potentially could accommodate the fatty acid chain of the LCO ligand. Two leucine residues (L147 and L154) were identified as the residues that give this patch its hydrophobic character. 
     To test the contribution of these two residues to LCO binding, both residues were replaced with similarly sized but negatively charged aspartate residues to produce NFP L147D L154D. Interestingly, the double mutated NFP L147D L154D ectodomain bound  S. meliloti  LCO-IV with approximately two times lower affinity; Kd of 48.0±1.0 μM ( FIG. 4B ). Closer inspection of the binding kinetics revealed that the association (K on ) was almost unaffected whereas the dissociation (K off ) was approximately 15 times faster in the double mutant. These results show that the hydrophobic patch of the NFP ectodomain is stabilizing the LCO bound state, and that this stabilization is most likely occurring via the fatty acid chain. Docking the LCO fatty acid in this hydrophobic patch and the chitin backbone in the LysM2 binding site (derived from CERK1) would place the sulphate and acetyl side groups facing K141. 
     Biochemical analysis of LCO binding to the hydrophobic patch mutant reveals that purified L147D/L154D NFP-ECD bound  S. meliloti  LCO-IV with 13-fold lower affinity (Kd of 166.7±4.2 μM) compared to WT NFP-ECD ( FIGS. 16A-16C ). The association rate (k on ) was 4.5-fold faster and the dissociation rate (k off ) was dramatically increased with 59-fold in the double mutant compared to the WT NFP-ECD, suggesting that the hydrophobic patch had a strong stabilizing effect on LCO binding mediated by the acyl chain. 
     The binding kinetics of AtCERK1 binding to chitin fragments were measured as a comparison. As shown in  FIGS. 17A-17B , fast association and dissociation rates were seen. These kinetics were reminiscent of the kinetics observed for the mutant L147D/L154D NFP-ECD ( FIG. 16B ). The binding kinetics of AtCERK1 to chitin fragments were clearly different than the binding kinetics of NFP to LCO ( FIG. 16A ). 
     Together, the data provided evidence that the hydrophobic patch in NFP (shown in  FIG. 16D ) was a conserved structural imprint critical for LCO perception and symbiotic signaling. 
     Example 6: Complementation Test in  Medicago  Nfp Mutants 
     To confirm the biochemical observations described in the previous examples, next a complementation test was performed in  Medicago  nfp mutants using hairy root transformation. 
     Materials and Methods 
     Complementation assay: Construct assembly, plant growth conditions, hairy root transformations, nodulation and ROS assays were generally conducted as described in Bozsoki et al. (2017) (Bozsoki Z, Cheng J, Feng F, Gysel K, Vinther M, Andersen KR, Oldroyd G, Blaise M, Radutoiu S, Stougaard J (2017) Receptor-mediated chitin perception in legume roots is functionally separable from Nod factor perception. Proc Natl Acad Sci 114: E8118-E8127). A general schematic of the construct is provided in  FIG. 5 . The tested transgenes were the mutated LysM receptors described in Example 5. In addition, NFP substitution variants replacing residues outside the hydrophobic patch in LysM2 (Q119F, K141E and T150H) or in LysM3 (T216F) were tested. 
     Results 
       FIG. 6A-6B  shows the results of the complementation test. The results shown in  FIG. 6A  are complementation tests where the plants were inoculated with  S. meliloti  strain 1021. When  Medicago  nfp mutants are transformed with the wild type Nfp gene, complementation is seen, which is defined as an average of 5 nodules per plant 49 days after inoculation with  S. meliloti  strain 1021. In contrast, roots transformed with the construct containing the double-mutated NFP L147D L154D (the surface residues that five NFP its hydrophobic character in LysM2) did not develop any nodules per plant after inoculation with  S. meliloti  strain 1021. Corresponding experiments with NFP substitution variants replacing residues outside the hydrophobic patch in LysM2 (Q119F, K141E and T150H) or in LysM3 (T216F) did not affect nodulation. 
     These complementation experiments were repeated using  S. medicae  inoculation, which has been reported to nodulate  Medicago  with higher efficiency. The results shown in  FIG. 6B  are complementation tests where the plants were inoculated with  S. medicae . The  S. medicae  results confirm that the construct containing the double-mutated NFP L147D L154D complements poorly. Taken together, these results show that the hydrophobic patch in NFP is required for LCO recognition, and for functional symbiotic signaling. 
     Example 7: Conservation of the Hydrophobic Patch 
     Previously, SYM10 in pea, NFR5 in  Lotus , and NFR5A in soybean had been shown to be crucial for LCO perception (see, e.g., Plant Cell Physiol. 2010 February; 51(2):201-14 and Madsen, E B et al. Nature. 2003 Oct. 9; 425(6958):637-40.). Therefore, homology modelling was used to determine whether the hydrophobic patch adjacent to LysM2 identified in  Medicago  NFP was a conserved feature across these proteins. In addition, homology modelling for  Lotus  LYS11 was done, and a crystal structure for  Lotus  LYS11 was obtained to verify the homology modelling results. 
     Materials and Methods 
     Modelling: Homology modelling was performed with SWISS-MODEL (Biasini 2014). The crystal structure of  Medicago  NFP served as the template model onto which the amino acid sequence of the target receptor was mapped. The output pdb filled structural model was generated and its electrostatic surface potential was calculated using the PDB2PQR and APBS webservers (PMID: 21425296). The results were visualized in PyMol using APBS tools 2.1 (DeLano, W. L. (2002). PyMOL. DeLano Scientific, San Carlos, Calif., 700.). 
     Crystal structure: Crystals of LYS11 were obtained using a vapour diffusion setup at 6.8 mg/mL in 0.1 M sodium malonate pH 6.0 and 12% PEG3350. Complete diffraction data was obtained and the phase problem was solved by molecular replacement using Phaser from the PHENIX suite with a homology model based on the AtCERK1 ectodomain structure (PDB coordinates 4EBZ) as a search model. Model building and refinement was done using COOT and the PHENIX suite, respectively. The output pdb filled structural model was generated and its electrostatic surface potential was calculated using the PDB2PQR and APBS webservers (PMID: 21425296). The results were visualized in PyMol using APBS tools 2.1 (DeLano, W. L. (2002). PyMOL. DeLano Scientific, San Carlos, Calif., 700.). 
     Results 
       FIG. 7A  shows homology modelling results for SYM10 in pea, NFR5 in  Lotus , and NFR5a in soybean. Homology modelling reveals that the hydrophobic patch is indeed present in the equivalent positions immediately below the LysM2 domain of these receptors. 
     To investigate the predictive power of this approach, the closest receptor homologs derived from the genomes of chickpea, bean, and peanut were also modelled ( FIG. 7B ). None of these receptor homologs has previously been functionally characterized. The hydrophobic patch in LysM2 is found to be conserved here as well, which predicts that these proteins are NFP/NFR5 type of LCO receptors. 
     Further, the diagnostic ability of modelling was tested in the  Medicago  NFP and  Lotus  NFR5 families of pseudokinases.  FIGS. 7C-7D  shows that  Medicago  LYR1 and  Lotus  LYS11 both contain the hydrophobic patch indicative of LCO receptor function, which is interesting in light of their putative role in AM symbiosis (See, e.g., Rasmussen, S R et al.  Sci Rep.  2016 Jul. 20; 6:29733 and Gomez, S K et al.  BMC Plant Biol.  2009 Jan. 22; 9:10.).  FIG. 7E  shows the predicted modeled of three LCO receptors:  Lotus  NFR5, Pea SYM10 and Soybean NFR5A. The models are shown as surfaces and colored in accordance with their electrostatic surface potential. The predicted hydrophobic patch is marked with a black dotted line and the C04 chitin molecule is show in the LysM2 ligand binding groove.  FIG. 7F  shows a comparison of two receptors lacking the hydrophobic patch,  Medicago  LYR3 and  Lotus  LYS12. 
     In order to experimentally validate the prediction that  Lotus  LYS11 had a hydrophobic patch comparable to NFP, the crystal structure of  Lotus  LYS11 was determined.  FIG. 7G  shows a comparison of the  Lotus  LYS11 model (left; also in  FIG. 7C ) with the crystal structure of  Lotus  LYS11 (right). From the electrostatic surface potential of the crystal structure, it was clear that LYS11 indeed contained a hydrophobic patch in LysM2 that was similar to the hydrophobic path in LysM2 of NFP. The presence of the hydrophobic domain, which had been predicted by modelling, in the actual structure of LYS11 determined by crystallography demonstrated the power of NFP-based modelling for identification of the hydrophobic patch in previously uncharacterized LCO receptor homologues. 
     Taken together, these results show that the hydrophobic patch is a conserved structural fingerprint found across NFP/NFR5 receptors (e.g., LCO receptors). The hydrophobic patch can therefore be used to predictively identify the class of NFP/NFR5 receptors in other legumes, which was not previously possible. 
     Example 8: Modelling of Non-Legume LCO Receptors of the NFP/NFR5 Class 
     Next, homology modelling was used to determine whether the hydrophobic patch adjacent to LysM2 identified in  Medicago  NFP was present in barley LysM receptor kinases. 
     Materials and Methods 
     Modelling: Homology modelling was performed with SWISS-MODEL (Biasini, M. et al. SWISS-MODEL: modelling protein tertiary and quaternary structure using evolutionary information.  Nucleic Acids Res.  42, W252-W258 (2014)). The crystal structure of  Medicago  NFP served as the template model onto which the amino acid sequence of the target receptor was mapped. The output pdb filled structural model was generated and its electrostatic surface potential was calculated using the PDB2PQR and APBS webservers (PMID: 21425296). The results were visualized in PyMol using APBS tools 2.1 (DeLano, W. L. (2002). PyMOL. DeLano Scientific, San Carlos, Calif., 700.). 
     Expression and purification of Barley RLK10 ectodomain: The  H. vulgare  RLK10 (HvRLK10; HvLysM-RLK10) ectodomain (residues 25-231; SEQ ID NO: 29) was codon-optimized for insect cell expression (Genscript, Piscataway, USA) and cloned into the pOET4 baculovirus transfer vector (Oxford Expression Technologies). The native RLK10 signal peptide was replaced with the gp64 signal peptide to facilitate secretion and a hexa-histidine (6×HIS) tag was added to the C-terminus to make the sequence HvRLK10-ecto (25-231), N-term gp64, C-term 6His (SEQ ID NO: 28). Recombinant baculoviruses were produced in Sf9 cells ( Spodoptera frugiperda ) using the FlashBac Gold kit (Oxford Expression technologies) according to the manufacturer&#39;s instructions with Lipofectin (ThermoFisher Scientific) as a transfection reagent. Protein expression was performed as follows. Suspension-cultured Sf9 cells were maintained with shaking at 299 K in serum-free MAX-XP (BD-Biosciences, discontinued) or HyClone SFX (GE Healthcare) medium supplemented with 1% Pen-Strep (10000 U/ml, Life technologies) and 1% CD lipid concentrate (Gibco). Protein expression was induced by adding recombinant passage 3 virus once the Sf9 cells reached a cell density of 1.0*10 7 {circumflex over ( )}6 cells/ml. After 5-7 days of expression, medium supernatant containing RLK10 ectodomains was harvested by centrifugation. This was followed by an overnight dialysis step against 50 mM Tris-HCl pH 8, 200 mM NaCl at 277 K. The RLK10 ectodomain was enriched by two subsequent steps of Ni-IMAC purification (HisTrap excel/HisTrap HP, both GE Healthcare). 
     Ligand binding tests: Ligand binding tests were performed using BLI as in Example 3. 
     Results 
     Homology modelling of all ten barley LysM receptor-like kinases (RLKs) was done using the  Medicago  NFP structure as a template. Of the barley LysM RLKs, HvRLK10 was the receptor that was closest to  Medicago  NFP and modelled the best using this approach.  FIG. 13B  shows homology modelling results for HvRLK10, which revealed that the hydrophobic patch was indeed present in the equivalent positions immediately below the LysM2 domain of this receptor. This clear hydrophobic patch indicated that HvRLK10 was a NFP/NFR5 type of LCO receptor. 
     To experimentally validate this prediction, the HvRLK10 ectodomain was expressed and purified for use in binding experiments (ectodomain schematic shown at top of  FIG. 13A ). The HvRLK10 ectodomain was shown to bind both  M. loti  LCO ( FIG. 13C ) and  S. meliloti  LCO ( FIG. 13D ). In contrast, the HvRLK10 ectodomain did not bind C05 ( FIG. 13A ). These binding studies showed that the HvRLK10 predicted to have a hydrophobic patch bound LCOs but not COs. 
     Taken together, these results show that the hydrophobic patch is a conserved structural fingerprint found across NFP/NFR5 receptors (e.g., LCO receptors). This conservation extends beyond the legume family into non-legume plants, such as barley. The hydrophobic patch can therefore be used to predictively identify the class of NFP/NFR5 receptors in non-legume plants, which was not previously possible.