bluuebunny/crossref_metadata_2025_split huggingface dataset:
Plants expressing thePtodisease resistance gene confer resistance to recombinant PVX containing the avirulence geneAvrPto
Authors: Tobias Christian M. , Oldroyd Giles E. D. , Chang Jeff H. , Staskawicz Brian J. 
Published: March 2003

Summary Elicitation of hypersensitive cell death and induction of plant disease resistance by

Pseudomonas syringae

pv.

tomato
(Pst) is dependent on activity of thePstHrp secretion system and the gene‐for‐gene interaction between the tomato resistance genePtoand the bacterial avirulence geneavrPto.AvrPtowas expressed transiently in resistant or susceptible plant lines via a potato virus X (PVX) vector. We found that while PVX is normally virulent on tomato, a PVX derivative expressingavrPtowas only capable of infecting plants lacking a functional Pto resistance pathway. Mutations in either thePtoorPrfgenes allowed systemic spread of the recombinant virus. These results indicate that recognition of AvrPto by Pto in resistant plant lines triggers a plant defense response that can confer resistance to a viral as well as a bacterial pathogen.
Regulation of a putative high‐affinity nitrate transporter (Nrt2;1At) in roots ofArabidopsis thaliana
Authors: Zhuo Degen , Okamoto Mamoru , Vidmar J. John , Glass Anthony D. M. 
Published: March 2003

SummaryPutative high‐affinity nitrate (NO3–) transporter genes, designatedNrt2;1AtandNrt2;2At, were isolated fromArabidopsis thalianaby RT–PCR using degenerate primers. The genes shared 86% and 89% identity at the amino acid and nucleotide levels, respectively, while their proteins shared 30–73% identities with other eukaryotic highaffinity NO3–transporters. Both genes were induced by NO3–, butNrt2;1Atgene expression was not apparent in 2‐ and 5‐day‐old plants. By 10 days, and thereafter,Nrt2;1Atgene expression in roots was substantially higher than for theNrt2;2Atgene. RootNrt2;1Atexpression levels were strongly correlated with inducible high‐affinity13NO3–influx into intact roots under several treatment conditions. The use of inhibitors of N assimilation indicated that downregulation ofNrt2;1Atexpression was mediated by NH4+, gln and other amino acids.
Potato StubSNF1 interacts with StubGAL83: a plant protein kinase complex with yeast and mammalian counterparts
Authors: Lakatos Lóránt , Klein Mathieu , Höfgen Rainer , Bánfalvi Zsófia 
Published: March 2003

Summary StubSNF1 is a potato cDNA that encodes a protein kinase similar to the yeast
SNF1
gene involved in transcriptional regulation of glucose‐repressible genes. The yeast SNF1 functions in a complex with GAL83/SIP1/SIP2 and SNF4 proteins. We have used StubSNF1 as bait in a yeast two‐hybrid system to screen for potato cDNAs encoding proteins that bind to StubSNF1. Three overlapping cDNAs, two different in size, were isolated. DNA sequence analysis revealed that they were orthologues of the yeast
GAL83/SIP1/SIP2
genes and their mammalian counterparts,
AMPK β
‐subunits. The direct interaction between the potato proteins StubGAL83 and StubSNF1 was shown by an
in vitro
binding assay. Southern and Northern hybridisations revealed that
StubGAL83
exists in a low copy number in the potato genome and is highly (but organ‐specifically) expressed in potato. In contrast,
StubSNF1
possesses low transcript levels in each organ, except in flowers where high amounts of StubSNF1 mRNA could be detected. We demonstrate here that StubGAL83 can also interact with yeast SNF4 in a yeast two‐hybrid system suggesting that plant SNF1 kinases may function in complexes similar to those detected in yeast and mammals.
Cytokinin oxidase from Zea mays: purification, cDNA cloning and expression in moss protoplasts
Authors: Houba‐Hérin Nicole , Pethe Claude , D’Alayer Jacques , Laloue Michel 
Published: March 2003

Summary Cytokinins are degraded by cytokinin oxidases (CKOs) which catalyse cleavage of the
N

6‐(isopent‐2‐enyl)‐side chain resulting in formation of adenine‐type compounds. CKO activity has been recorded in many plants and is thought to play a key role in controlling cytokinin levels in plants. Several partially purified CKOs have been characterised but no genes have been isolated yet. CKO activity is known to be inhibited by phenylureas, cytokinin agonists. We used 1‐(2‐azido‐6‐chloropyrid‐4‐yl)‐3‐(4‐[3H])phenylurea ([3H]‐azidoCPPU) to photolabel a glycosylated CKO from maize kernels. This enabled us to purify the enzyme. Peptide sequences were determined and the corresponding cDNA was cloned. The deduced amino acid sequence shares homology domains with FAD‐dependent oxidases. An original assay based on transient expression of the enzyme in moss protoplasts allowed the functionality of the recombinant enzyme to be demonstrated.
The helicase domain of the TMV replicase proteins induces the N‐mediated defence response in tobacco
Authors: Les Erickson F. , Holzberg Steve , Calderon‐Urrea Alejandro , Handley Vanessa , Axtell Michael , Corr Catherine , Baker Barbara 
Published: March 2003

SummaryTobacco mosaic virus (TMV) induces the hypersensitive response (HR) in tobacco plants containing the N gene. This defence response is characterized by cell death at the site of virus infection and inhibition of viral replication and movement. A previous study indicated that a portion of the TMV replicase containing a putative helicase domain is involved in HR induction. Here, this observation is confirmed and extended by showing that non‐viral expression of a 50 kDa TMV helicase fragment (p50) is sufficient to induce the N‐mediated HR in tobacco. Like the HR elicited by TMV infection, transgenic expression of p50 induces a temperature‐sensitive defence response. We demonstrate that recombinant p50 protein has ATPase activity, as suggested by the presence of conserved sequence motifs found in ATPase/helicase enzymes. A point mutation that alters one of these motifs abolishes ATPase activity in vitro but does not affect HR induction. These results suggest that features of the TMV helicase domain, independent of its enzymatic activity, are recognized by N‐containing tobacco to induce TMV resistance.
The Arabidopsis flowering‐time gene LUMINIDEPENDENS is expressed primarily in regions of cell proliferation and encodes a nuclear protein that regulates LEAFY expression
Authors: Aukerman Milo J.. , Lee Ilha , Weigel Detlef , Amasino Richard M.. 
Published: March 2003

SummaryMutations in the LUMINIDEPENDENS ( LD) gene of Arabidopsis thaliana (L.) Heynh. (Arabidopsis) confer a late‐flowering phenotype, indicating that LD normally functions to promote the floral transition. RNA and protein blot analyses, along with the analysis of transgenic plants containing a fusion between a genomic fragment of LD and the reporter gene uidA ( GUS), indicate that LD is expressed primarily in apical proliferative regions of the shoot and root, including the shoot apical meristem and leaf primordia. Subcellular localization studies indicate that LD is a nuclear protein, consistent with its previously proposed transcriptional regulatory role. We have also found that in an apetala1 cauliflower ( ap1 cal) background the ld mutation converts the reproductive shoot apex to a more vegetative state, a phenotype that is similar to that seen for the leafy ( lfy) mutant. Furthermore, in situ hybridization analysis indicates that LFY levels are drastically reduced at the apex of ld ap1 cal plants after bolting. These data are consistent with the idea that at least one function of LD is to participate in the regulation of LFY.
FPF1 modulates the competence to flowering in Arabidopsis
Authors: Melzer Siegbert , Kampmann Grit , Chandler John , Apel Klaus 
Published: March 2003

SummaryDuring the transition to flowering the FPF1 gene is expressed in the peripheral zone of apical meristems and in floral meristems of Arabidopsis. Constitutive expression of FPF1 causes early flowering in Arabidopsis under both long‐day and short‐day conditions and leads to a shortened juvenile phase as measured by the trichome distribution on the abaxial leaf surface. In the classical late flowering mutants, overexpression of FPF1 compensates partially for the late flowering phenotype, indicating that FPF1 acts downstream or in a parallel pathway to the mutated genes. The co‐overexpression of 35S::AP1 with 35S::FPF1 leads to a synergistic effect on the shortening of the time to flowering under short‐day conditions. The co‐overexpression of 35S::FPF1 and 35S::LFY, however, shows only an additive reduction of flowering time and the conversion of nearly every shoot meristem, except the inflorescence meristem, to a floral meristem under the same light conditions. In addition, the constitutive expression of FPF1 attenuates the severe lfy‐1 phenotype under short days and phenocopies to a great extent the lfy‐1 mutant grown under long‐day conditions. Thus, we assume that FPF1 modulates the competence to flowering of apical meristems.
Three 4‐coumarate:coenzyme A ligases in Arabidopsis thaliana represent two evolutionarily divergent classes in angiosperms
Authors: Ehlting Jürgen , Büttner Daniela , Wang Qing , Douglas Carl J. , Somssich Imre E. , Kombrink Erich 
Published: March 2003

SummaryThe enzyme 4‐coumarate:CoA ligase (4CL) plays a key role in channelling carbon flow into diverse branch pathways of phenylpropanoid metabolism which serve important functions in plant growth and adaptation to environmental perturbations. Here we report on the cloning of the 4CL gene family from Arabidopsis thaliana and demonstrate that its three members, At4CL1, At4CL2 and At4CL3, encode isozymes with distinct substrate preference and specificities. Expression studies revealed a differential behaviour of the three genes in various plant organs and upon external stimuli such as wounding and UV irradiation or upon challenge with the fungus, Peronospora parasitica. Phylogenetic comparisons indicate that, in angiosperms, 4CL can be classified into two major clusters, class I and class II, with the At4CL1 and At4CL2 isoforms belonging to class I and At4CL3 to class II. Based on their enzymatic properties, expression characteristics and evolutionary relationships, At4CL3 is likely to participate in the biosynthetic pathway leading to flavonoids whereas At4CL1 and At4CL2 are probably involved in lignin formation and in the production of additional phenolic compounds other than flavonoids.
The Pib gene for rice blast resistance belongs to the nucleotide binding and leucine‐rich repeat class of plant disease resistance genes
Authors: Wang Zi‐Xuan , Yano Masahiro , Yamanouchi Utako , Iwamoto Masao , Monna Lisa , Hayasaka Hiroshi , Katayose Yuichi , Sasaki Takuji 
Published: March 2003

SummaryRice blast, caused by the fungal pathogen Magnaporthe grisea, is one of the most serious diseases of rice. Here we describe the isolation and characterization of Pib, one of the rice blast resistance genes. The Pib gene was isolated by a map‐based cloning strategy. The deduced amino acid sequence of the Pib gene product contains a nucleotide binding site (NBS) and leucine‐rich repeats (LRRs); thus, Pib is a member of the NBS‐LRR class of plant disease resistance genes. Interestingly, a duplication of the kinase 1a, 2 and 3a motifs of the NBS region was found in the N‐terminal half of the Pib protein. In addition, eight cysteine residues are clustered in the middle of the LRRs, a feature which has not been reported for other R genes. Pib gene expression was induced upon altered environmental conditions, such as altered temperatures and darkness.
Cloning and expression of a cDNA encoding homospermidine synthase from Senecio vulgaris (Asteraceae) in Escherichia coli
Authors: Kaiser Annette 
Published: March 2003

SummaryThe enzyme homospermidine synthase catalyzes the NAD+‐dependent conversion of 2 mol putrescine into homospermidine. Instead of putrescine, spermidine can substitute for the first putrescine moiety in plants, in which case diaminopropane instead of ammonia is released. The enzyme facilitates the formation of the ‘uncommon’ polyamine homospermidine which is an important precursor in the biosynthesis of pyrrolizidine alkaloids. The first plant homospermidine synthase was purified to apparent chemical homogenity from the root tissue culture Senecio vernalis (Asteraceae) (Böttcher et al. 1994, Can. J. Chem. 72, 80–85; Ober 1997, Dissertation). Four endopeptidase LysC fragments were sequenced from the purified protein. With the aid of degenerate primers against these peptides, a cDNA encoding homospermidine synthase was now cloned and characterized from Senecio vulgaris. The nucleotide sequence of the cloned cDNA revealed an open reading frame of 1155‐base pairs containing 385 amino acids with a predicted Mr of 44500. GenBank research revealed that the deduced amino acid sequence shows 59% identity to human deoxyhypusine synthase. The homospermidine synthase encoding cDNA was subcloned into the expression vector pet15b and overexpressed in E. coli. The recombinant enzyme formed upon expression catalyzed homospermidine synthesis.
An apospory‐specific genomic region is conserved between Buffelgrass (Cenchrus ciliaris L.) and Pennisetum squamulatum Fresen
Authors: Roche Dominique , Cong Peisheng , Chen Zhenbang , Hanna Wayne W. , Gustine David L. , Sherwood Robert T. , Ozias‐Akins Peggy 
Published: March 2003

SummaryTwelve molecular markers linked to pseudogamous apospory, a form of gametophytic apomixis, were previously isolated from Pennisetum squamulatum Fresen. No recombination between these markers was found in a segregating population of 397 individuals (Ozias‐Akins et al. 1998, Proc. Natl Acad. Sci. USA, 95, 5127–5132). The objective of the present study was to test if these markers were also linked to the aposporous mode of reproduction in two small segregating populations of Cenchrus ciliaris (= Pennisetum ciliare (L.)Link), another apomictic grass species. Among 12 markers (sequence characterized amplified regions, SCARs), six were scored as dominant markers between aposporous and sexual C. ciliaris genotypes (presence/absence, respectively). Five were always linked to apospory and one showed a low level of recombination in 84 progenies. Restriction fragment length polymorphisms (RFLPs) were observed between sexual and apomictic phenotypes for three of the six remaining SCARs from P. squamulatum when used as probes. No recombination was observed in the F1 progenies. Preliminary data from megabase DNA analysis and sequencing in both species indicate that an apospory‐specific genomic region (ASGR) is highly conserved between the two species. Although C. ciliaris has a smaller genome size to P. squamulatum, a higher copy number for markers linked to apospory found in the former may impair the progress of positional cloning of gene(s) for apomixis in this species.
The liguleless2 gene of maize functions during the transition from the vegetative to the reproductive shoot apex
Authors: Walsh Justine , Freeling Michael 
Published: March 2003

SummaryDuring a maize plant’s (Zea mays) development, the shoot apical meristem (SAM) generates an apex that proceeds through different phases: juvenile vegetative, adult vegetative and reproductive. During each phase the structures produced are distinguishable from structures produced during the other phases. In this paper, we demonstrate that the LIGULELESS2 (LG2) function is required for an accurate vegetative to reproductive phase transition. The maize gene liguleless2 (lg2) has been shown to encode a basic‐leucine zipper (bZIP) protein and to function in narrowing the region from which the ligule and auricle develop in a typical maize leaf. Here we show that lg2 mutant plants can have reduced long tassel branches, extra vegetative leaves and extra husk leaves when compared to wild‐type siblings. This indicates a role for the lg2 gene in the vegetative to reproductive phase transition of the shoot apex. We also discuss a potential role for the lg2 gene in general phase transition processes.
The Arabidopsis thaliana TAG1 mutant has a mutation in a diacylglycerol acyltransferase gene
Authors: Zou Jitao , Wei Yangdou , Jako Colette , Kumar Arvind , Selvaraj Gopalan , Taylor David C. 
Published: March 2003

SummaryIn Arabidopsis thaliana (ecotype Columbia) mutant line AS11, an EMS‐induced mutation at a locus on chromosome II results in a reduced diacylglycerol acyltransferase (DGAT; EC 2.3.1.20) activity, reduced seed triacylglycerol, an altered seed fatty acid composition, and delayed seed development. A mutation has been identified in AS11 in a gene, which we designated as TAG1, that encodes a protein with an amino acid sequence which is similar to a recently reported mammalian DGAT, and, to a lesser extent, to acyl CoA:cholesterol acyltransferases. Molecular analysis revealed that the mutant allele in AS11 has a 147 bp insertion located at the central region of intron 2. At the RNA level, an 81 bp insertion composed entirely of an exon 2 repeat was found in the transcript. While the seed triacylglycerol content is reduced by the lesion in AS11, there is no apparent effect on sterol ester content in the mutant seed. The TAG1 cDNA was over‐expressed in yeast, and its activity as a microsomal DGAT confirmed. Therefore, the TAG1 locus encodes a diacylglycerol acyltransferase, and the insertion mutation in the TAG1 gene in mutant AS11 results in its altered lipid phenotype.
Cross‐talk between wound signalling pathways determines local versus systemic gene expression in Arabidopsis thaliana
Authors: Rojo Enrique , León José , Sánchez‐Serrano José J. 
Published: March 2003

SummaryPlants react to mechanical damage by activating a set of genes, the products of which are thought to serve defensive functions. In solanaceous plants, cell wall‐derived oligosaccharides and the plant hormones jasmonic acid and ethylene participate in the signalling network for wound‐induced expression of proteinase inhibitors and other defence‐related genes, both in the locally damaged and in the systemic non‐damaged leaves. Here we show that in Arabidopsis thaliana, these signalling components interact in novel ways to activate distinct responses. In damaged tissues, oligosaccharides induce the expression of a specific set of wound‐responsive genes while repressing jasmonic acid‐responsive genes that are activated in the systemic tissues. The oligosaccharide‐mediated repression of the jasmonic acid‐dependent signalling pathway is exerted through the production and perception of ethylene in the locally damaged tissue. This cross‐talk between separate wound signalling pathways thus allows the set up of different responses in the damaged and the systemic tissues of plants reacting to injury.
Distinct osmo‐sensing protein kinase pathways are involved in signalling moderate and severe hyper‐osmotic stress
Authors: Munnik Teun , Ligterink Wilco , Meskiene Irute , Calderini Ornella , Beyerly John , Musgrave Alan , Hirt Heribert 
Published: March 2003

SummaryPlant growth is severely affected by hyper‐osmotic salt conditions. Although a number of salt‐induced genes have been isolated, the sensing and signal transduction of salt stress is little understood. We provide evidence that alfalfa cells have two osmo‐sensing protein kinase pathways that are able to distinguish between moderate and extreme hyper‐osmotic conditions. A 46 kDa protein kinase was found to be activated by elevated salt concentrations (above 125 mm NaCl). In contrast, at high salt concentrations (above 750 mm NaCl), a 38 kDa protein kinase, but not the 46 kDa kinase, became activated. By biochemical and immunological analysis, the 46 kDa kinase was identified as SIMK, a member of the family of MAPKs (mitogen‐activated protein kinases). SIMK is not only activated by NaCl, but also by KCl and sorbitol, indicating that the SIMK pathway is involved in mediating general hyper‐osmotic conditions. Salt stress induces rapid but transient activation of SIMK, showing maximal activity between 8 and 16 min before slow inactivation. When inactive, most mammalian and yeast MAPKs are cytoplasmic but undergo nuclear transloca‐ tion upon activation. By contrast, SIMK was found to be a constitutively nuclear protein and the activity of the kinase was not correlated with changes in its intra‐cellular compartmentation, suggesting an intra‐nuclear mechanism for the regulation of SIMK activity.
Transient expression of members of the germin‐like gene family in epidermal cells of wheat confers disease resistance
Authors: Schweizer Patrick , Christoffel Andreas , Dudler Robert 
Published: March 2003

SummaryThe wheat genome encodes a family of germin‐like proteins that differ with respect to regulation and tissue specificity of expression of the corresponding genes. While germin exhibits oxalate oxidase (E.C. 1.2.3.4.) activity, the germin‐like proteins (GLPs) have no known enzymatic activity. A role of oxalate oxidase in plant defence has been proposed, based on the capacity of the enzyme to produce H2O2, a reactive oxygen species. The role in defence of germin and other members of the germin‐like gene family was functionally assessed in a transient assay system based on particle bombardment of wheat leaves. Transient expression of the pathogen‐induced germin gf‐2.8 gene, but not of the constitutively expressed HvGLP1 gene, reduced the penetration efficiency of Blumeria (syn. Erysiphe) graminis f.sp. tritici, the causal agent of wheat powdery mildew, on transformed cells. Two engineered germin‐gf‐2.8 genes and the TaGLP2a gene, which all encoded proteins without oxalate oxidase activity, also reduced the penetration efficiency of the fungus, demonstrating that oxalate oxidase activity is not required for conferring enhanced resistance. Instead, activity tagging experi‐ments showed that in cells transiently expressing the germin gf‐2.8 gene, the transgene product became insolubilised at sites of attempted fungal penetration where localised production of H2O2 was observed. Thus, germin and GLPs may play a structural role in cell‐wall re‐enforcement during pathogen attack.
Molecular domains of the cellulose/xyloglucan network in the cell walls of higher plants
Authors: Pauly Markus , Albersheim Peter , Darvill Alan , York William S. 
Published: March 2003

SummaryCellulose and xyloglucan (XG) assemble to form the cellulose/XG network, which is considered to be the dominant load‐bearing structure in the growing cell walls of non‐graminaceous land plants. We have extended the most commonly accepted model for the macromolecular organization of XG in this network, based on the structural and quantitative analysis of three distinct XG fractions that can be differentially extracted from the cell walls isolated from etiolated pea stems. Approximately 8% of the dry weight of these cell walls consists of XG that can be solubilized by treatment of the walls with a XG‐specific endoglucanase (XEG). This material corresponds to an enzyme‐susceptible XG domain, proposed to form the cross‐links between cellulose microfibrils. Another 10% of the cell wall consists of XG that can be solubilized by concentrated KOH after XEG treatment. This material constitutes another XG domain, proposed to be closely associated with the surface of the cellulose microfibrils. An additional 3% of the cell wall consists of XG that can be solubilized only when the XEG‐ and KOH‐treated cell walls are treated with cellulase. This material constitutes a third XG domain, proposed to be entrapped within or between cellulose microfibrils. Analysis of the three fractions indicates that metabolism is essentially limited to the enzyme‐susceptible domain. These results support the hypothesis that enzyme‐catalyzed modification of XG cross‐links in the cellulose/XG network is required for the growth and development of the primary plant cell wall, and demonstrate that the structural consequences of these metabolic events can be analyzed in detail.