bluuebunny/crossref_metadata_2025_split huggingface dataset:
ACGT‐containing abscisic acid response element (ABRE) and coupling element 3 (CE3) are functionally equivalent
Authors: Hobo Tokunori , Asada Mihoko , Kowyama Yasuo , Hattori Tsukaho 
Published: March 2003

SummaryACGT‐containing ABA response elements (ABREs) have been functionally identified in the promoters of various genes. In addition, single copies of ABRE have been found to require a cis‐acting, coupling element to achieve ABA induction. A coupling element 3 (CE3) sequence, originally identified as such in the barley HVA1 promoter, is found approximately 30 bp downstream of motif A (ACGT‐containing ABRE) in the promoter of the Osem gene. The relationship between these two elements was further defined by linker‐scan analyses of a 55 bp fragment of the Osem promoter, which is sufficient for ABA‐responsiveness and VP1 activation. The analyses revealed that both motif A and CE3 sequence were required not only for ABA‐responsiveness but also for VP1 activation. Since the sequences of motif A and CE3 were found to be similar, motif‐exchange experiments were carried out. The experiments demonstrated that motif A and CE3 were interchangeable by each other with respect to both ABA and VP1 regulation. In addition, both sequences were shown to be recognized by a VP1‐interacting, ABA‐responsive bZIP factor TRAB1. These results indicate that ACGT‐containing ABREs and CE3 are functionally equivalent cis‐acting elements. Furthermore, TRAB1 was shown to bind two other non‐ACGT ABREs. Based on these results, all these ABREs including CE3 are proposed to be categorized into a single class of cis‐acting elements.
Natural allelic variation identifies new genes in the Arabidopsis circadian system
Authors: Swarup Kamal , Alonso‐Blanco Carlos , Lynn James R. , Michaels Scott D. , Amasino Richard M. , Koornneef Maarten , Millar Andrew J. 
Published: March 2003

SummaryWe have analysed the circadian rhythm of Arabidopsis thaliana leaf movements in the accession Cvi from the Cape Verde Islands, and in the commonly used laboratory strains Columbia (Col) and Landsberg (erecta) (Ler), which originated in Northern Europe. The parental lines have similar rhythmic periods, but the progeny of crosses among them reveal extensive variation for this trait. An analysis of 48 Ler/Cvi recombinant inbred lines (RILs) and a further 30 Ler/Col RILs allowed us to locate four putative quantitative trait loci (QTLs) that control the period of the circadian clock. Near‐isogenic lines (NILs) that contain a QTL in a small, defined chromo‐ somal region allowed us to confirm the phenotypic effect and to map the positions of three period QTLs, designated ESPRESSO, NON TROPPO and RALENTANDO. Quantitative trait loci at the locations of RALENTANDO and of a fourth QTL, ANDANTE, were identified in both Ler/Cvi and Ler/Col RIL populations. Some QTLs for circadian period are closely linked to loci that control flowering time, including FLC. We show that flc mutations shorten the circadian period such that the known allelic variation in the MADS‐box gene FLC can account for the ANDANTE QTL. The QTLs ESPRESSO and RALENTANDO identify new genes that regulate the Arabidopsis circadian system in nature, one of which may be the flowering‐time gene GIGANTEA.
Unsaturated fatty acids inhibit MP2C, a protein phosphatase 2C involved in the wound‐induced MAP kinase pathway regulation
Authors: Baudouin Emmanuel , Meskiene Irute , Hirt Heribert 
Published: March 2003

SummaryWhen mechanically injured, plants develop multiple defense systems including the activation of specific genes. These responses are triggered by a complex network of signalling events that include Ca2+ fluxes, the production of free fatty acids from membrane lipids, as well as the activation of mitogen‐activated protein kinases (MAPK). In the present paper, we address the question of the regulation of the MAPK pathway by wound‐induced Ca2+ and fatty acid signals. We report that MP2C, a serine/threonine protein phosphatase 2C from alfalfa involved in MAPK pathway inactivation, is inhibited specifically in vitro by long‐carbon‐chain polyunsaturated fatty acids, and α‐linolenic acid, the primary product of the octadecanoid pathway, was found to be the most potent inhibitor. Ca2+ also inhibits MP2C, but only at high concentrations, and other divalent cations show similar inhibitory effect, making it unlikely that Ca2+ is involved in the regulation of MP2C in vivo. Overall, our data suggest that cross‐talk between wound‐induced MAPK and octadecanoid pathways may occur at the level of protein phosphatase 2C and linolenic acid.
Agrobacterium transient expression system as a tool for the isolation of disease resistance genes: application to the Rx2 locus in potato
Authors: Bendahmane Abdelhafid , Querci Maddalena , Kanyuka Konstantin , Baulcombe David C. 
Published: March 2003

Summary Rx2 confers resistance against potato virus X (PVX). To clone Rx2, we developed a system based on Agrobacterium‐mediated transient expression of candidate R genes in transgenic tobacco leaves expressing the PVX coat protein elicitor of Rx2‐mediated resistance. Using this system, a potato gene eliciting HR specifically in the presence of the elicitor was identified. Based on genetical and functional analysis, it is concluded that the cloned gene is Rx2. The transient expression system is potentially adaptable to cloning of any other resistance gene. The Rx2 locus is on chromosome V of potato and the encoded protein is highly similar to the products of Rx1 and Rxh1 encoded on potato chromosome XII. Rxh1 has been shown elsewhere to encode a potato cyst nematode resistance gene Gpa2. All three proteins are in the leucine zipper‐nucleotide binding site‐leucine rich repeat class of resistance gene products. Rx1 and Rx2 are functionally identical and are almost identical in the C terminal region consistent with a role of the leucine rich repeats in recognition of the PVX coat protein. In the N terminal, half there are some regions where the Rx1 and Rx2 proteins are more similar to each other than to the Rxh1 protein. However, in other regions these proteins are more similar to Rxh1 than to each other. Based on this mosaic pattern of sequence similarity, we conclude that sequence exchange occurs repeatedly between genetically unlinked disease resistance genes through a process of gene conversion.
Induction of competence for elicitation of defense responses in cucumber hypocotyls requires proteasome activity
Authors: Becker Jürgen , Kempf Ralf , Jeblick Wolfgang , Kauss Heinrich 
Published: March 2003

SummaryThe epidermal cells of hypocotyls from etiolated cucumber seedlings are not constitutively competent for elicitation of the rapid H2O2 defense response. However, elicitor competence developed while conditioning the surface‐abraded seedlings by rotating them in buffer for 4 h. Competence development was greatly potentiated by inducers of systemic acquired resistance and suppressed by specific inhibitors of proteasome activity, clasto‐lactacystin β‐lactone (LAC) and carboxybenzoyl‐
l‐leucyl‐
l‐leucyl‐
l‐leucinal (LLL). In the freshly abraded seedlings, chitinase gene activation became evident approximately 4 h after elicitor addition. Accumulation of chitinase mRNA was enhanced upon conditioning prior to elicitation and was inhibited by LAC and LLL, indicating that the process which leads to H2O2 elicitation competence is also superimposed on the elicitation of chitinase mRNA. LAC and LLL caused an accumulation of ubiquitin‐conjugated proteins and enhanced the expression of a proteasome α‐subunit, suggesting that proteasome activity was specifically inhibited and that the effect observed on gene expression was not due to impaired gene induction in general. Together, our results suggest that the ubiquitin–proteasome system may play a crucial role in a process which switches the signaling pathway for diverse plant defense responses into a functional state, as is known for many basic cellular processes in both animals and yeast.
Arabidopsis thaliana SHAGGY‐related protein kinases (AtSK11 and 12) function in perianth and gynoecium development
Authors: Dornelas Marcelo C. , Van Lammeren Andie A. M. , Kreis Martin 
Published: March 2003

SummaryIn higher plants, the correct patterning of the floral meristem in terms of organ type, number and form is the result of a concerted expression of a network of genes. We describe phenotypes of flower patterning, resulting from a reduction of transcript levels of the Arabidopsis SHAGGY‐related protein kinase genes AtSK11(ASKα) and AtSK12(ASKγ). The AtSK genes are plant homologues of the Drosophila shaggy (SGG) gene and the mammalian Glycogen‐Synthase Kinase‐3 (GSK‐3). The SGG protein kinase is a key component of the wingless signalling pathway and is required for the establishment of tissue patterning and cell fate determination. The expression patterns of the AtSK11(ASKα) and AtSK12(ASKγ) genes during wild‐type Arabidopsis inflorescence development, detected by in situ hybridisation, have been shown to be consistent with a possible role in floral meristem patterning. AtSK11(ASKα) and AtSK12(ASKγ) transcripts were detected at the periphery of the inflorescence meristem and in the floral meristem. At later stages the expression of the AtSK genes became localised in specific regions of developing flower organ primordia. Furthermore, we have obtained and analysed transgenic plants containing AtSK11(ASKα) and AtSK12(ASKγ) gene specific antisense constructs. These plants developed flowers showing a higher number of perianth organs and an alteration of the apical‐basal patterning of the gynoecium.
Arbuscular mycorrhizal fungi induce the non‐mevalonate methylerythritol phosphate pathway of isoprenoid biosynthesis correlated with accumulation of the ‘yellow pigment’ and other apocarotenoids
Authors: Walter Michael H. , Fester Thomas , Strack Dieter 
Published: March 2003

SummaryPlants and certain bacteria use a non‐mevalonate alternative route for the biosynthesis of many isoprenoids, including carotenoids. This route has been discovered only recently and has been designated the deoxyxylulose phosphate pathway or methylerythritol phosphate (MEP) pathway. We report here that colonisation of roots from wheat, maize, rice and barley by the arbuscular mycorrhizal fungal symbiont Glomus intraradices involves strong induction of transcript levels of two of the pivotal enzymes of the MEP pathway, 1‐deoxy‐D‐xylulose 5‐phosphate synthase (DXS) and 1‐deoxy‐D‐xylulose 5‐phosphate reductoisomerase (DXR). This induction is temporarily and spatially correlated with specific and concomitant accumulation of two classes of apocarotenoids, namely glycosylated C13 cyclohexenone derivatives and mycorradicin (C14) conjugates, the latter being a major component of the long‐known ‘yellow pigment’. A total of six cyclohexenone derivatives were characterised from mycorrhizal wheat and maize roots. Furthermore, the acyclic structure of mycorradicin described previously only from maize has been identified from mycorrhizal wheat roots after alkaline treatment of an ‘apocarotenoid complex’ of yellow root constituents. We propose a hypothetical scheme for biogenesis of both types of apocarotenoids from a common oxocarotenoid (xanthophyll) precursor. This is the first report demonstrating (i) that the plastidic MEP pathway is active in plant roots and (ii) that it can be induced by a fungus.
Phytochrome A resets the circadian clock and delays tuber formation under long days in potato
Authors: Yanovsky Marcelo J. , Izaguirre Miriam , Wagmaister Javier A. , Gatz Christiane , Jackson Stephen D. , Thomas Brian , Casal Jorge J. 
Published: March 2003

SummaryTransgenic potatoes (Solanum tuberosum) with either increased (sense transformants) or reduced (antisense transformants) phytochrome A (phyA) levels were used, in combination with specific light treatments, to investigate the involvement of phyA in the perception of signals that entrain the circadian clock. Far‐red or far‐red plus red light treatments given during the night reset the circadian rhythm of leaf movements in wild‐type plants and phyA over‐expressors, but had little effect in phyA under‐expressors. Far‐red light was also able to reset the rhythm of leaf movement in wild‐type Arabidopsis thaliana but was not effective in mutants without phyA. Blue light was necessary to reset the rhythm in phyA‐deficient potato plants. Resetting of the rhythm by far‐red plus red light was only slightly affected in transgenic plants with reduced levels of phytochrome B. The production of tubers was delayed by day extensions with far‐red plus red light, but this effect was reduced in transgenic lines deficient in phyA. We conclude that phyA is involved in resetting the circadian clock controlling leaf movements and in photoperiod sensing in light‐grown potato plants.
Soluble phospholipase A2 activity is induced before oxylipin accumulation in tobacco mosaic virus‐infected tobacco leaves and is contributed by patatin‐like enzymes
Authors: Dhondt Sandrine , Geoffroy Pierrette , Stelmach Boguslawa A. , Legrand Michel , Heitz Thierry 
Published: March 2003

SummaryRecent evidence suggests that oxidized lipid‐derived molecules play significant roles in inducible plant defence responses against microbial pathogens, either by directly deterring parasite multiplication, or as signals involved in the induction of sets of defence genes. The synthesis of these oxylipins was hypothesized to be initiated by the phospholipase A2‐mediated release of unsaturated fatty acids from membrane lipids. Here, we demonstrate that, in tobacco leaves reacting hypersensitively to tobacco mosaic virus, a strong increase in soluble phospholipase A2 (PLA2) activity occurs at the onset of necrotic lesion appearance. This rapid PLA2 activation occurred before the accumulation of 12‐oxophytodienoic and jasmonic acids, two fatty acid‐derived defence signals. Three PLA2 isoforms were separated and the most active enzyme was partially purified, its N‐terminal sequence displaying similarity with patatin, the major storage protein in potato tubers. Three related tobacco patatin‐like cDNAs, called NtPat1, NtPat2 and NtPat3, were cloned, with NtPat2 encoding the PLA2 isolated from infected leaves. RT–PCR experiments showed a rapid transcriptional activation of the three NtPat genes in virus‐infected leaves, preceding the increase in PLA2 activity. Recombinant NtPat1 and NtPat3 enzymes were active in an assay using labelled bacterial membranes, and also displayed high bona fide PLA2 activity on phosphatidylcholine substrate. These results point to a possible new role of patatin‐like phospholipases in inducible plant defence responses. The induction kinetics together with the enzymatic activity data indicate that the NtPat proteins may provide precursors for oxylipin synthesis during the hypersensitive response to pathogens.
The Arabidopsis SUCROSE UNCOUPLED‐6 gene is identical to ABSCISIC ACID INSENSITIVE‐4: involvement of abscisic acid in sugar responses
Authors: Huijser Casper , Kortstee Anne , Pego Jónatas , Weisbeek Peter , Wisman Ellen , Smeekens Sjef 
Published: March 2003

SummaryIn plants, sugars act as signalling molecules that control many aspects of metabolism and development. Arabidopsis plants homozygous for the recessive sucrose uncoupled‐6 (sun6) mutation show a reduced sensitivity to sugars for processes such as photosynthesis, gene expression and germination. The sun6 mutant is insensitive to sugars that are substrates for hexokinase, suggesting that SUN6 might play a role in hexokinase‐dependent sugar responses. The SUN6 gene was cloned by transposon tagging and analysis showed it to be identical to the previously described ABSCISIC ACID INSENSITIVE‐4 (ABI4) gene. Our analysis suggests the involvement of abscisic acid and components of the abscisic acid signal transduction cascade in a hexokinase‐dependent sugar response pathway. During the plant life cycle, SUN6/ABI4 may be involved in controlling metabolite availability in an abscisic acid‐ and sugar‐dependent way.
The Arabidopsis sugar‐insensitive mutants sis4 and sis5 are defective in abscisic acid synthesis and response
Authors: Laby Ron J. , Kincaid M. Sean , Kim Donggiun , Gibson Susan I. 
Published: March 2003

SummaryAlthough soluble sugar levels affect many aspects of plant development and physiology, little is known about the mechanisms by which plants respond to sugar. Here we report the isolation of 13 sugar‐insensitive (sis) mutants of Arabidopsis that, unlike wild‐type plants, are able to form expanded cotyledons and true leaves when germinated on media containing high concentrations of glucose or sucrose. The sis4 and sis5 mutants are allelic to the ABA‐biosynthesis mutant aba2 and the ABA‐insensitive mutant abi4, respectively. In addition to being insensitive to glucose and sucrose, the sis4/aba2 and sis5/abi4 mutants also display decreased sensitivity to the inhibitory effects of mannose on early seedling development. Mutations in the ABI5 gene, but not mutations in the ABI1, ABI2 or ABI3 genes, also lead to weak glucose‐ and mannose‐insensitive phenotypes. Wild‐type and mutant plants show similar responses to the effects of exogenous sugar on chlorophyll and anthocyanin accumulation, indicating that the mutants are not defective in all sugar responses. These results indicate that defects in ABA metabolism and some, but not all, defects in ABA response can also alter response to exogenous sugar.
A zinc finger protein RHL41 mediates the light acclimatization response in Arabidopsis
Authors:   Asako Iida, Kazuoka Toru , Torikai Satomi , Kikuchi Hiromi , Oeda Kenji 
Published: March 2003

Summary Arabidopsis thaliana plants showed an increased tolerance to high‐intensity light when pre‐exposed to medium‐intensity light. This response, known as light acclimatization, depended on the quantity of light, the period of irradiation, and the quality of light. Among characterized acclimatization‐induced cDNA clones, we identified a zinc finger protein rhl41 (responsive to high light) gene, that was rapidly up‐regulated in proportion to the time of irradiation and the light intensity. Transgenic Arabidopsis plants over‐expressing the rhl41 gene showed an increased tolerance to high‐intensity light, and also morphological changes of thicker and dark green leaves. Interestingly, the palisade parenchyma was highly developed in the leaves of the transgenic plants, which is one of the long‐term acclimatization responses in Arabidopsis plants. The anthocyanin content (a light protectant) as well as the chlorophyll content also increased. Antisense transgenic plants exhibited decreased tolerance to high irradiation. We propose that the RHL41 zinc finger protein has a key role in the acclimatization response to changes in light intensity.
A potato α‐glucosidase gene encodes a glycoprotein‐processing α‐glucosidase II‐like activity. Demonstration of enzyme activity and effects of down‐regulation in transgenic plants
Authors: Taylor* Mark A. , Ross Heather A. , McRae Diane , Stewart Derek , Roberts Ian , Duncan George , Wright Frank , Millam Steve , Davies Howard V. 
Published: March 2003

SummaryIn order to elucidate more fully the function of a potato gene (MAL1) encoding α‐glucosidase activity, transgenic plants in which MAL1 expression was down‐regulated were generated using antisense technology. In transgenic lines severely down‐regulated in the expression of MAL1, total α‐glucosidase activity was not decreased in leaves and tubers, and the contents of starch, glucose, fructose and sucrose remained unchanged in tubers. Phylogenetic analysis indicated that the MAL1 gene product was more similar to the glycoprotein‐processing α‐glucosidase II of mammalian and yeast origin than to other plant α‐glucosidases. Using [14C‐Glc]‐labelled Glc2Man9GlcNAc2 as a substrate, it was demonstrated that glucosidase II activity was markedly down‐regulated in microsomes isolated from tubers of four independent antisense lines studied in detail, strongly suggesting that MAL1 encodes glucosidase II activity. In field trials (but not in the glasshouse), MAL1 down‐regulation produced an extremely stunted phenotype – the leaves were curled and tuber yield was decreased by 90% compared to control values. Microscopic analysis of leaves revealed significant differences between the antisense and control samples. Plants with down‐regulated glucosidase II activity showed a greater degree of plasmolysis, and an increase in the size of mesophyll intracellular spaces. Analysis of cell walls also indicated changes in structure as a result of MAL1 down‐regulation. In leaves from four antisense lines, the steady‐state transcript level corresponding to the endoplasmic reticulum chaperone, BiP, was enhanced. This is diagnostic of stress in the endoplasmic reticulum.
Metabolic engineering of beta‐carotene and lycopene content in tomato fruit
Authors: Rosati Carlo , Aquilani Riccardo , Dharmapuri Sridhar , Pallara Patrizia , Marusic Carla , Tavazza Raffaela , Bouvier Florence , Camara Bilal , Giuliano Giovanni 
Published: March 2003

SummaryRipe tomato fruits accumulate large amounts of the red linear carotene, lycopene (a dietary antioxidant) and small amounts of its orange cyclisation product, beta‐carotene (pro‐vitamin A). Lycopene is transformed into beta‐carotene by the action of lycopene beta‐cyclase (β‐Lcy). We introduced, via Agrobacterium‐mediated transformation, DNA constructs aimed at up‐regulating (OE construct) or down‐regulating (AS construct) the expression of the β‐Lcy gene in a fruit‐specific fashion. Three transformants containing the OE construct show a significant increase in fruit beta‐carotene content. The fruits from these plants display different colour phenotypes, from orange to orange‐red, depending on the lycopene/beta‐carotene ratio. Fruits from AS transformants show up to 50% inhibition of β‐Lcy expression, accompanied by a slight increase in lycopene content. Leaf carotenoid composition is unaltered in all transformants. In most transformants, an increase in total carotenoid content is observed with respect to the parental line. This increase occurs in the absence of major variations in the expression of endogenous carotenoid genes.
Identification of an Arabidopsis thaliana mutant accumulating threonine resulting from mutation in a new dihydrodipicolinate synthase gene
Authors: Sarrobert Catherine , Thibaud Marie‐Christine , Contard‐David Pascale , Gineste Sandrine , Bechtold Nicole , Robaglia Christophe , Nussaume Laurent 
Published: March 2003

SummaryA novel Arabidopsis DHDPS gene named DHDPS2 was found through identification of a mutant by promoter trapping. The mutation promotes a reduction of growth resulting from combination of a defect in lysine biosynthesis and accumulation of a toxic level of threonine or derived products. The mutant also modifies the amino acid composition issuing from the pyruvate and aspartate pathways, affecting mainly the root compartment. These data are in accordance with the expression of DHDPS2 in the root apex as visualized by expression of the GUS reporter gene. This suggests that a large proportion of the amino acids derived from pyruvate and aspartate are synthesized in this organ.