| arabidopsis is susceptible to infection by a downy mildew fungus. | a population of arabidopsis thaliana growing locally in a suburb of zürich called weiningen was observed to be infected with downy mildew. plants were collected and the progress of infection was investigated in artificial inoculations in the laboratory. the plants proved to be highly susceptible, and pronounced intercellular mycelial growth, haustoria formation, conidiophore production, and sporulation of the causal organism peronospora parasitica were all observed. the formation of oogonia, ant ... | 1990 | 2152169 |
| laboratory tests of fungicides against peronospora parasitica (pers. ex fr.) fr. | | 1968 | 5705483 |
| genetics of brassica rapa (syn. campestris). 2. multiple disease resistance to three fungal pathogens: peronospora parasitica, albugo candida and leptosphaeria maculans. | although the genetic basis of multiple disease resistance (mdr) is poorly understood, it is of great value for understanding the evolution of disease resistance in natural plant populations and for increasing crop yields in agriculture. in brassica rapa, we studied genetic correlations among levels of disease resistance to three fungal pathogens: peronospora parasitica, albugo candida and leptosphaeria maculans. a large, replicated quantitative genetics experiment used artificial selection on re ... | 1995 | 7591832 |
| a mutation in arabidopsis that leads to constitutive expression of systemic acquired resistance. | systemic acquired resistance (sar) is a nonspecific defense response in plants that is associated with an increase in the endogenous level of salicylic acid (sa) and elevated expression of pathogenesis-related (pr) genes. to identify mutants involved in the regulation of pr genes and the onset of sar, we transformed arabidopsis with a reporter gene containing the promoter of a beta-1,3-glucanase-encoding pr gene (bgl2) and the coding region of beta-glucuronidase (gus). the resulting transgenic l ... | 1994 | 7866028 |
| systemic acquired resistance in arabidopsis requires salicylic acid but not ethylene. | systemic acquired resistance (sar) is an inducible plant response to infection by a necrotizing pathogen. in the induced plant, sar provides broad-spectrum protection against not only the inducing pathogen, but also against other, unrelated pathogens. both salicylic acid (sa) and sar-gene expression have been implicated as playing important roles in the initiation and maintenance of sar. here, we describe the characterization of transgenic arabidopsis plants that express the bacterial nahg gene ... | 1995 | 8664495 |
| phenotypic and genotypic variation in the interaction between arabidopsis thaliana and albugo candida. | two biotrophic parasites of the wild crucifer arabidopsis thaliana (l.) heynh, are being used to explore the molecular basis and evolution of genotype-spcific recognition and host defense. genes for recognition of peronospora parasitica (downy mildew) are numerous in a. thaliana and located on four of the five chromosomes as described previously. genes for recognition of the closely related parasite albugo candida (white blister) are described here. in contrast to teh former parasite, less than ... | 1995 | 8664502 |
| four arabidopsis rpp loci controlling resistance to the noco2 isolate of peronospora parasitica map to regions known to contain other rpp recognition specificities. | interactions between arabidopsis thaliana and the downy mildew fungus peronospora parasitica provide a model system to study the genetic and molecular basis of plant-pathogen recognition. with the use of the noco2 isolate of p. parasitica, the reaction phenotypes of 46 accessions of arabidopsis were examined and 31 accessions exhibited resistance. resistance phenotypes examined ranged from distinct necrotic pits or flecks to a weak necrosis accompanied by late and sparse fungal sporulation. segr ... | 1996 | 8755623 |
| benzothiadiazole induces disease resistance in arabidopsis by activation of the systemic acquired resistance signal transduction pathway. | benzothiadiazole (bth) is a novel chemical activator of disease resistance in tobacco, wheat and other important agricultural plants. in this report, it is shown that bth works by activating sar in arabidopsis thaliana. bth-treated plants were resistant to infection by turnip crinkle virus, pseudomonas syringae pv 'tomato' dc3000 and peronospora parasitica. chemical treatment induced accumulation of mrnas from the sar-associated genes, pr-1, pr-2 and pr-5. bth treatment induced both pr-1 mrna ac ... | 1996 | 8758979 |
| characterization of eds1, a mutation in arabidopsis suppressing resistance to peronospora parasitica specified by several different rpp genes. | the interaction between arabidopsis and the biotrophic oomycete peronospora parasitica (downy mildew) provides an attractive model pathosystem to identify molecular components of the host that are required for genotype-specific recognition of the parasite. these components are the so-called rpp genes (for resistance to p. parasitica). mutational analysis of the ecotype wassilewskija (ws-0) revealed an rpp-nonspecific locus called eds1 (for enhanced disease susceptibility) that is required for th ... | 1996 | 8953768 |
| phytoalexin-deficient mutants of arabidopsis reveal that pad4 encodes a regulatory factor and that four pad genes contribute to downy mildew resistance. | we are working to determine the role of the arabidopsis phytoalexin, camalexin, in protecting the plant from pathogen attack by isolating phytoalexin-deficient (pad) mutants in the accession columbia (col-0) and examining their response to pathogens. mutations in pad1, pad2, and pad4 caused enhanced susceptibility to the bacterial pathogen pseudomonas syringae pv. maculicola strain es4326 (psmes4326), while mutations in pad3 or pad5 did not. camalexin was not detected in any of the double mutant ... | 1997 | 9136026 |
| the arabidopsis downy mildew resistance gene rpp5 shares similarity to the toll and interleukin-1 receptors with n and l6. | plant disease resistance genes operate at the earliest steps of pathogen perception. the arabidopsis rpp5 gene specifying resistance to the downy mildew pathogen peronospora parasitica was positionally cloned. it encodes a protein that possesses a putative nucleotide binding site and leucine-rich repeats, and its product exhibits striking structural similarity to the plant resistance gene products n and l6. like n and l6, the rpp5 n-terminal domain resembles the cytoplasmic domains of the drosop ... | 1997 | 9212464 |
| the cpr5 mutant of arabidopsis expresses both npr1-dependent and npr1-independent resistance. | the cpr5 mutant was identified from a screen for constitutive expression of systemic acquired resistance (sar). this single recessive mutation also leads to spontaneous expression of chlorotic lesions and reduced trichome development. the cpr5 plants were found to be constitutively resistant to two virulent pathogens, pseudomonas syringae pv maculicola es4326 and peronospora parasitica noco2; to have endogenous expression of the pathogenesis-related gene 1 (pr-1); and to have an elevated level o ... | 1997 | 9338960 |
| uncoupling pr gene expression from npr1 and bacterial resistance: characterization of the dominant arabidopsis cpr6-1 mutant. | in arabidopsis, npr1 mediates the salicylic acid (sa)-induced expression of pathogenesis-related (pr) genes and systemic acquired resistance (sar). here, we report the identification of another component, cpr 6, that may function with npr1 in regulating pr gene expression. the dominant cpr 6-1 mutant expresses the sa/npr1-regulated pr genes (pr-1, bgl 2, and pr-5) and displays enhanced resistance to pseudomonas syringae pv maculicola es4326 and peronospora parasitica noco2 in the absence of sar ... | 1998 | 9548982 |
| generation of broad-spectrum disease resistance by overexpression of an essential regulatory gene in systemic acquired resistance. | the recently cloned npr1 gene of arabidopsis thaliana is a key regulator of acquired resistance responses. upon induction, npr1 expression is elevated and the npr1 protein is activated, in turn inducing expression of a battery of downstream pathogenesis-related genes. in this study, we found that npr1 confers resistance to the pathogens pseudomonas syringae and peronospora parasitica in a dosage-dependent fashion. overexpression of npr1 leads to enhanced resistance with no obvious detrimental ef ... | 1998 | 9601001 |
| different requirements for eds1 and ndr1 by disease resistance genes define at least two r gene-mediated signaling pathways in arabidopsis. | the arabidopsis genes eds1 and ndr1 were shown previously by mutational analysis to encode essential components of race-specific disease resistance. here, we examined the relative requirements for eds1 and ndr1 by a broad spectrum of resistance (r) genes present in three arabidopsis accessions (columbia, landsberg-erecta, and wassilewskija). we show that there is a strong requirement for eds1 by a subset of r loci (rpp2, rpp4, rpp5, rpp21, and rps4), conferring resistance to the biotrophic oomyc ... | 1998 | 9707643 |
| three genes of the arabidopsis rpp1 complex resistance locus recognize distinct peronospora parasitica avirulence determinants. | plant resistance (r) genes have evolved specific recognition capabilities in defense against pathogens. the evolution of r gene function and maintenance of r gene diversity within a plant species are therefore of great interest. in the arabidopsis accession wassilewskija, the rpp1 region on chromosome 3 contains four genetically linked recognition specificities, conditioning resistance to different isolates of the biotrophic oomycete peronospora parasitica (downy mildew). we show that three of f ... | 1998 | 9811793 |
| intragenic recombination and diversifying selection contribute to the evolution of downy mildew resistance at the rpp8 locus of arabidopsis. | pathogen resistance (r) genes of the nbs-lrr class (for nucleotide binding site and leucine-rich repeat) are found in many plant species and confer resistance to a diverse spectrum of pathogens. little is known about the mechanisms that drive nbs-lrr gene evolution in the host-pathogen arms race. we cloned the rpp8 gene (for resistance to peronospora parasitica) and compared the structure of alleles at this locus in resistant landsberg erecta (ler-0) and susceptible columbia (col-0) accessions. ... | 1998 | 9811794 |
| impaired fungicide activity in plants blocked in disease resistance signal transduction. | fungicide action is generally assumed to be dependent on an antibiotic effect on a target pathogen, although a role for plant defense mechanisms as mediators of fungicide action has not been excluded. here, we demonstrate that in arabidopsis, the innate plant defense mechanism contributes to the effectiveness of fungicides. in nahg and nim1 (for noninducible immunity) arabidopsis plants, which normally exhibit increased susceptibility to pathogens, the fungicides metalaxyl, fosetyl, and cu(oh)2 ... | 1998 | 9811797 |
| differential expression of a senescence-enhanced metallothionein gene in arabidopsis in response to isolates of peronospora parasitica and pseudomonas syringae. | the metallothionein gene, lsc54, shows increased expression during leaf senescence in brassica napus and arabidopsis thaliana. a number of abiotic and biotic stresses have been shown to induce senescence-like symptoms in plants and, to investigate this further, the promoter of the lsc54 gene was cloned and fused to the gus gene and transformed into arabidopsis. the promoter was highly induced during leaf senescence and also in response to wounding; histochemical analysis indicated that this indu ... | 1998 | 9839466 |
| separate jasmonate-dependent and salicylate-dependent defense-response pathways in arabidopsis are essential for resistance to distinct microbial pathogens. | the endogenous plant hormones salicylic acid (sa) and jasmonic acid (ja), whose levels increase on pathogen infection, activate separate sets of genes encoding antimicrobial proteins in arabidopsis thaliana. the pathogen-inducible genes pr-1, pr-2, and pr-5 require sa signaling for activation, whereas the plant defensin gene pdf1.2, along with a pr-3 and pr-4 gene, are induced by pathogens via an sa-independent and ja-dependent pathway. an arabidopsis mutant, coi1, that is affected in the ja-res ... | 1998 | 9844023 |
| suppressors of the arabidopsis lsd5 cell death mutation identify genes involved in regulating disease resistance responses. | cell death is associated with the development of the plant disease resistance hypersensitive reaction (hr). arabidopsis lsd mutants that spontaneously exhibit cell death reminiscent of the hr were identified previously. to study further the regulatory context in which cell death acts during disease resistance, one of these mutants, lsd5, was used to isolate new mutations that suppress its cell death phenotype. using a simple lethal screen, nine lsd5 cell death suppressors, designated phx (for th ... | 1999 | 9872969 |
| identification of three putative signal transduction genes involved in r gene-specified disease resistance in arabidopsis. | the rps5 disease resistance gene of arabidopsis mediates recognition of pseudomonas syringae strains that possess the avirulence gene avrpphb. by screening for loss of rps5-specified resistance, we identified five pbs (avrpphb susceptible) mutants that represent three different genes. mutations in pbs1 completely blocked rps5-mediated resistance, but had little to no effect on resistance specified by other disease resistance genes, suggesting that pbs1 facilitates recognition of the avrpphb prot ... | 1999 | 10224270 |
| inhibition of protoporphyrinogen oxidase expression in arabidopsis causes a lesion-mimic phenotype that induces systemic acquired resistance. | we have used an antisense expression technology in arabidopsis based on the yeast gal4/uas transactivation system (guyer et al., genetics, 1998; 149:633-639) to reduce levels of protoporphyrinogen ix oxidase (ppo), the last common enzyme of the biosynthesis of the haem group and chlorophyll. plants expressing the antisense ppo gene presented growth alterations and their leaves showed necrotic lesions that appeared similar to lesions characteristic of the pathogen-induced hypersensitive reaction, ... | 1999 | 10230064 |
| three 4-coumarate:coenzyme a ligases in arabidopsis thaliana represent two evolutionarily divergent classes in angiosperms. | the 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 beh ... | 1999 | 10417722 |
| salicylic acid induction-deficient mutants of arabidopsis express pr-2 and pr-5 and accumulate high levels of camalexin after pathogen inoculation. | in arabidopsis, systemic acquired resistance against pathogens has been associated with the accumulation of salicylic acid (sa) and the expression of the pathogenesis-related proteins pr-1, pr-2, and pr-5. we report here the isolation of two nonallelic mutants impaired in the pathway leading to sa biosynthesis. these sa induction-deficient (sid) mutants do not accumulate sa after pathogen inoculation and are more susceptible to both virulent and avirulent forms of pseudomonas syringae and perono ... | 1999 | 10449575 |
| deficiency in phytoalexin production causes enhanced susceptibility of arabidopsis thaliana to the fungus alternaria brassicicola. | the phytoalexin-deficient arabidopsis mutant pad3-1, which is affected in the production of the indole-type phytoalexin camalexin, has previously been shown not to display altered susceptibility to either the bacterium pseudomonas syringae (glazebrook & ausubel 1994; proc. natl. acad. sci. usa, 91: 8955-8959) or the biotrophic fungi peronospora parasitica (glazebrook et al. 1997; genetics, 146: 381-392) and erysiphe orontii (reuber et al. 1998; plant j. 16: 473-485). we now show that this mutant ... | 1999 | 10476063 |
| genetic and physical mapping of the rpp13 locus, in arabidopsis, responsible for specific recognition of several peronospora parasitica (downy mildew) isolates. | fifteen isolates of the biotrophic oomycete peronospora parasitica (downy mildew) were obtained from a population of arabidopsis thaliana plants that established naturally in a garden the previous year. they exhibited phenotypic variation in a set of 12 arabidopsis accessions that suggested that the parasite population consisted of at least six pathotypes. one isolate, maks9, elicited an interaction phenotype of flecking necrosis and no sporulation (fn) in the arabidopsis accession nd-1, and mor ... | 1999 | 10494631 |
| pronounced intraspecific haplotype divergence at the rpp5 complex disease resistance locus of arabidopsis. | in arabidopsis ecotype landsberg erecta (ler), rpp5 confers resistance to the pathogen peronospora parasitica. rpp5 is part of a clustered multigene family encoding nucleotide binding-leucine-rich repeat (lrr) proteins. we compared 95 kb of dna sequence carrying the ler rpp5 haplotype with the corresponding 90 kb of arabidopsis ecotype columbia (col-0). relative to the remainder of the genome, the ler and col-0 rpp5 haplotypes exhibit remarkable intraspecific polymorphism. the rpp5 gene family p ... | 1999 | 10559437 |
| harpin induces disease resistance in arabidopsis through the systemic acquired resistance pathway mediated by salicylic acid and the nim1 gene. | harpin, the product of the hrpn gene of erwinia amylovora, elicits the hypersensitive response and disease resistance in many plants. harpin and known inducers of systemic acquired resistance (sar) were tested on five genotypes of arabidopsis thaliana to assess the role of sar in harpin-induced resistance. in wild-type plants, harpin elicited systemic resistance to peronospora parasitica and pseudomonas syringae pv. tomato, accompanied by induction of the sar genes pr-1 and pr-2. however, in exp ... | 1999 | 10571880 |
| requirement of functional ethylene-insensitive 2 gene for efficient resistance of arabidopsis to infection by botrytis cinerea. | inoculation of wild-type arabidopsis plants with the fungus alternaria brassicicola results in systemic induction of genes encoding a plant defensin (pdf1.2), a basic chitinase (pr-3), and an acidic hevein-like protein (pr-4). pathogen-induced induction of these three genes is almost completely abolished in the ethylene-insensitive arabidopsis mutant ein2-1. this indicates that a functional ethylene signal transduction component (ein2) is required in this response. the ein2-1 mutants were found ... | 1999 | 10594097 |
| isolation and characterization of powdery mildew-resistant arabidopsis mutants. | a compatible interaction between a plant and a pathogen is the result of a complex interplay between many factors of both plant and pathogen origin. our objective was to identify host factors involved in this interaction. these factors may include susceptibility factors required for pathogen growth, factors manipulated by the pathogen to inactivate or avoid host defenses, or negative regulators of defense responses. to this end, we identified 20 recessive arabidopsis mutants that do not support ... | 2000 | 10677553 |
| identification of arabidopsis mutants exhibiting an altered hypersensitive response in gene-for-gene disease resistance. | a mutational study was carried out to isolate arabidopsis thaliana plants that exhibit full or partial disruption of the rps2-mediated hypersensitive response (hr) to pseudomonas syringae that express avrrpt2. five classes of mutants were identified including mutations at rps2, dnd mutations causing a "defense, no death" loss-of-hr phenotype, a lesion-mimic mutant that also exhibited an hr- phenotype, and a number of intermediate or partial-loss-of-hr mutants. surprisingly, many of these mutants ... | 2000 | 10707353 |
| rpp13 is a simple locus in arabidopsis thaliana for alleles that specify downy mildew resistance to different avirulence determinants in peronospora parasitica. | disease resistance (r) genes are found in plants as either simple (single allelic series) loci, or more frequently as complex loci of tandemly repeated genes. these different loci are likely to be under similar evolutionary forces from pathogens, but the contrast between them suggests important differences in mechanisms associated with dna structure and recombination that generate and maintain r gene diversity. the rpp13 locus in arabidopsis represents an important paradigm for studying the evol ... | 2000 | 10743658 |
| members of the arabidopsis hrt/rpp8 family of resistance genes confer resistance to both viral and oomycete pathogens. | turnip crinkle virus (tcv) inoculation onto tcv-resistant arabidopsis leads to a hypersensitive response (hr) controlled by the dominant gene hrt. hrt is a member of the class of resistance (r) genes that contain a leucine zipper, a nucleotide binding site, and leucine-rich repeats. the chromosomal position of hrt and its homology to resistance gene rpp8 and two rpp8 homologs indicate that unequal crossing over and gene conversion may have contributed to hrt evolution. rpp8 confers resistance to ... | 2000 | 10810142 |
| downy mildew (peronospora parasitica) resistance genes in arabidopsis vary in functional requirements for ndr1, eds1, npr1 and salicylic acid accumulation. | to better understand the genetic requirements for r gene-dependent defense activation in arabidopsis, we tested the effect of several defense response mutants on resistance specified by eight rpp genes (for resistance to peronospora parasitica) expressed in the col-0 background. in most cases, resistance was not suppressed by a mutation in the sar regulatory gene npr1 or by expression of the nahg transgene. thus, salicylic acid accumulation and npr1 function are not necessary for resistance medi ... | 2000 | 10886772 |
| cdna-aflp display for the isolation of peronospora parasitica genes expressed during infection in arabidopsis thaliana. | to identify genes from the obligatory biotrophic oomycete peronospora parasitica that are expressed during infection in arabidopsis thaliana we employed cdna-amplified fragment length polymorphism (aflp) display. cdna-aflp fragments from infected and non-infected leaves were separated in parallel by gel electrophoresis and displayed by autoradiography. most differential gene fragments were derived from p. parasitica. | 2000 | 10939263 |
| a comparison of peronospora parasitica (downy mildew) isolates from arabidopsis thaliana and brassica oleracea using amplified fragment length polymorphism and internal transcribed spacer 1 sequence analyses. | amplified fragment length polymorphism (aflp) fingerprints and internal transcribed spacer 1 (its1) sequences from 27 peronospora parasitica isolates (collected from arabidopsis thaliana or brassica oleracea), 5 albugo candida isolates (from the same hosts and from capsella bursa-pastoris), and 1 bremia lactucae isolate (from lactuca sativa) were compared. the aflp analysis divided the isolates into five groups that correlated with taxonomic species and, in most cases, with host origin. the only ... | 2000 | 11017765 |
| active oxygen species as mediators of plant immunity: three case studies. | a burst of active oxygen species (aos) is known to be involved in local cell death as part of plant defence against pathogens. it is, however, under dispute to what extent aos can induce pathogen resistance and immunity throughout the plant. three experimental strategies that reveal a primary role for aos and a surprisingly low chemical and spatial specificity are now described for tobacco and arabidopsis thaliana plants. ozone is a gaseous aos that was applied to non-transgenic plants. hydrogen ... | 2000 | 11030422 |
| potentiation of pathogen-specific defense mechanisms in arabidopsis by beta -aminobutyric acid. | the nonprotein amino acids gamma-aminobutyric acid (gaba) and beta-aminobutyric acid (baba) have known biological effects in animals and plants. their mode of action has been the object of thorough research in animals but remains unclear in plants. our objective was to study the mode of action of baba in the protection of arabidopis plants against virulent pathogens. baba protected arabidopsis against the oomycete pathogen peronospora parasitica through activation of natural defense mechanisms o ... | 2000 | 11058166 |
| three unique mutants of arabidopsis identify eds loci required for limiting growth of a biotrophic fungal pathogen. | to identify components of the defense response that limit growth of a biotrophic fungal pathogen, we isolated arabidopsis mutants with enhanced disease susceptibility to erysiphe orontii. our initial characterization focused on three mutants, eds14, eds15, and eds16. none of these is considerably more susceptible to a virulent strain of the bacterial pathogen pseudomonas syringae pv. maculicola (psm). all three mutants develop a hypersensitive response when infiltrated with psm expressing the av ... | 2000 | 11069695 |
| manipulation of salicylate content in arabidopsis thaliana by the expression of an engineered bacterial salicylate synthase. | salicylic acid (sa) plays a central role as a signalling molecule involved in plant defense against microbial attack. genetic manipulation of sa biosynthesis may therefore help to generate plants that are more disease-resistant. by fusing the two bacterial genes pcha and pchb from pseudomonas aeruginosa, which encode isochorismate synthase and isochorismate pyruvate-lyase, respectively, we have engineered a novel hybrid enzyme with salicylate synthase (sas) activity. the pchb-a fusion was expres ... | 2001 | 11169183 |
| probenazole induces systemic acquired resistance in arabidopsis with a novel type of action. | probenazole (pbz; 3-allyloxy-1,2-benzisothiazole-1,1-dioxide), which is the active ingredient in oryzemate, has been used widely in asia to protect rice plants against the rice blast fungus magnaporthe grisea. to study pbz's mode of action, we analyzed its ability, as well as that of its active metabolite 1, 2-benzisothiazol-3 (2h)-one 1,1-dioxide (bit) to induce defense gene expression and resistance in arabidopsis mutants that are defective in various defense signaling pathways. wild-type arab ... | 2001 | 11169191 |
| the arabidopsis downy mildew resistance gene, rpp13-nd, functions independently of ndr1 and eds1 and does not require the accumulation of salicylic acid. | rpp13-nd-mediated resistance prevents parasitism by five isolates of peronospora parasitica (at) in a transgenic arabidopsis. columbia background. we tested the effect of a number of known disease resistance mutations on the rpp13-nd function and found that resistance remained unaltered in plants carrying mutations in either eds1 or ndr1 and in double ndr1-1/eds1-2 mutant lines. furthermore, we found that pbs2, pad4-1, npr1-1, and rps5-1, which compromise resistance to a number of p. parasitica ... | 2001 | 11277440 |
| study of the role of antimicrobial glucosinolate-derived isothiocyanates in resistance of arabidopsis to microbial pathogens. | crude aqueous extracts from arabidopsis leaves were subjected to chromatographic separations, after which the different fractions were monitored for antimicrobial activity using the fungus neurospora crassa as a test organism. two major fractions were obtained that appeared to have the same abundance in leaves from untreated plants versus leaves from plants challenge inoculated with the fungus alternaria brassicicola. one of both major antimicrobial fractions was purified to homogeneity and iden ... | 2001 | 11299350 |
| a recessive mutation in the arabidopsis ssi2 gene confers sa- and npr1-independent expression of pr genes and resistance against bacterial and oomycete pathogens. | the arabidopsis thaliana npr1 gene is required for salicylic acid (sa)-induced expression of pathogenesis-related (pr) genes and systemic acquired resistance. however, loss-of-function mutations in npr1 do not confer complete loss of pr gene expression or disease resistance. thus these responses also can be activated via an npr1-independent pathway that currently remain to be elucidated. the ssi2-1 mutant, identified in a genetic screen for suppressors of npr1-5, affects signaling through the np ... | 2001 | 11309146 |
| abnormal callose response phenotype and hypersusceptibility to peronospoara parasitica in defence-compromised arabidopsis nim1-1 and salicylate hydroxylase-expressing plants. | to investigate the impact of induced host defenses on the virulence of a compatible peronospora parasitica strain on arabidopsis thaliana, we examined growth and development of this pathogen in nim1-1 mutants and transgenic salicylate hydroxylase plants. these plants are unable to respond to or accumulate salicylic acid (sa), respectively, are defective in expression of systemic acquired resistance (sar), and permit partial growth of some normally avirulent pathogens. we dissected the p. parasit ... | 2001 | 11310731 |
| constitutive salicylic acid-dependent signaling in cpr1 and cpr6 mutants requires pad4. | salicylic acid (sa)-dependent signaling controls activation of a set of plant defense mechanisms that are important for resistance to a variety of microbial pathogens. many arabidopsis mutants that display altered sa-dependent signaling have been isolated. we used double mutant analysis to determine the relative positions of the pad4, cpr1, cpr5, cpr6, dnd1 and dnd2 mutations in the signal transduction network leading to sa-dependent activation of defense gene expression and disease resistance. ... | 2001 | 11439127 |
| environmentally sensitive, sa-dependent defense responses in the cpr22 mutant of arabidopsis. | to investigate the signaling pathways through which defense responses are activated following pathogen infection, we have isolated and characterized the cpr22 mutant. this plant carries a semidominant, conditional lethal mutation that confers constitutive expression of the pathogenesis-related (pr) genes pr-1, pr-2, pr-5 and the defensin gene pdf1.2. cpr22 plants also display spontaneous lesion formation, elevated levels of salicylic acid (sa) and heightened resistance to peronospora parasitica ... | 2001 | 11439131 |
| a fatty acid desaturase modulates the activation of defense signaling pathways in plants. | salicylic acid (sa) plays an important role in activating various plant defense responses, including expression of the pathogenesis-related (pr) genes and systemic acquired resistance. a critical positive regulator of the sa signaling pathway in arabidopsis is encoded by the npr1 gene. however, there is growing evidence that npr1-independent pathways can also activate pr expression and disease resistance. to elucidate the components associated with npr1-independent defense signaling, we isolated ... | 2001 | 11481500 |
| a humidity-sensitive arabidopsis copine mutant exhibits precocious cell death and increased disease resistance. | the copines are a newly identified class of calcium-dependent, phospholipid binding proteins that are present in a wide range of organisms, including paramecium, plants, caenorhabditis elegans, mouse, and human. however, the biological functions of the copines are unknown. here, we describe a humidity-sensitive copine mutant in arabidopsis. under nonpermissive, low-humidity conditions, the cpn1-1 mutant displayed aberrant regulation of cell death that included a lesion mimic phenotype and an acc ... | 2001 | 11595798 |
| activation of an eds1-mediated r-gene pathway in the snc1 mutant leads to constitutive, npr1-independent pathogen resistance. | the arabidopsis npr1 protein is an essential regulatory component of systemic acquired resistance (sar). mutations in the npr1 gene completely block the induction of sar by signals such as salicylic acid (sa). an arabidopsis mutant, snc1 (suppressor of npr1-1, constitutive 1), was isolated in a screen for suppressors of npr1-1. in the npr1-1 background, the snc1 mutation resulted in constitutive resistance to pseudomonas syringae maculicola es4326 and peronospora parasitica noco2. high levels of ... | 2001 | 11605952 |
| salicylic acid and nim1/npr1-independent gene induction by incompatible peronospora parasitica in arabidopsis. | to identify pathogen-induced genes distinct from those involved in systemic acquired resistance, we used cdna-amplified fragment length polymorphism to examine rna levels in arabidopsis thaliana wild type, nim1-1, and salicylate hydroxylase-expressing plants after inoculation with an incompatible isolate of the downy mildew pathogen peronospora parasitica. fifteen genes are described, which define three response profiles on the basis of whether their induction requires salicylic acid (sa) accumu ... | 2001 | 11605963 |
| ndr1, a locus of arabidopsis thaliana that is required for disease resistance to both a bacterial and a fungal pathogen. | we have employed arabidopsis thaliana as a model host plant to genetically dissect the molecular pathways leading to disease resistance. a. thaliana accession col-0 is susceptible to the bacterial pathogen pseudomonas syringae pv. tomato strain dc3000 but resistant in a race-specific manner to dc3000 carrying any one of the cloned avirulence genes avrb, avrrpm1, avrrpt2, and avrpph3. fast-neutron-mutagenized col-0 m2 seed was screened to identify mutants susceptible to dc3000(avrb). disease assa ... | 1995 | 11607554 |
| arabidopsis signal transduction mutant defective in chemically and biologically induced disease resistance. | plants possess multiple resistance mechanisms that guard against pathogen attack. among these are inducible systems such as systemic acquired resistance (sar). sar is activated by pathogen exposure and leads to an increase in salicylic acid (sa), high-level expression of sar-related genes, and resistance to a spectrum of pathogens. to identify components of the signal transduction pathways regulating sar, a mutant screen was developed that uses 2,6-dichloroisonicotinic acid as an activator of sa ... | 1995 | 11607555 |
| the promoter of a basic pr1-like gene, atprb1, from arabidopsis establishes an organ-specific expression pattern and responsiveness to ethylene and methyl jasmonate. | antimicrobial proteins are a key feature underlying the deployment of both pre-formed and inducible defence responses. probably the most well characterised class are the pathogenesis-related (pr) proteins, which are found in both basic and acidic isoforms. here we describe the isolation and characterisation of a gene, designated atprb1, encoding a basic pr1-like protein from arabidopsis. this protein showed high amino acid sequence identity with basic and acidic pr1 proteins from other plant spe ... | 2001 | 11725949 |
| arabidopsis gp91phox homologues atrbohd and atrbohf are required for accumulation of reactive oxygen intermediates in the plant defense response. | reactive oxygen intermediates (roi) are strongly associated with plant defense responses. the origin of these roi has been controversial. arabidopsis respiratory burst oxidase homologues (rboh genes) have been proposed to play a role in roi generation. we analyzed lines carrying dspm insertions in the highly expressed atrbohd and atrbohf genes. both are required for full roi production observed during incompatible interactions with the bacterial pathogen pseudomonas syringae pv. tomato dc3000(av ... | 2002 | 11756663 |
| pathogen stress increases somatic recombination frequency in arabidopsis. | evolution is based on genetic variability and subsequent phenotypic selection. mechanisms that modulate the rate of mutation according to environmental cues, and thus control the balance between genetic stability and flexibility, might provide a distinct evolutionary advantage. stress-induced mutations stimulated by unfavorable environments, and possible mechanisms for their induction, have been described for several organisms, but research in this area has mainly focused on microorganisms. we h ... | 2002 | 11836502 |
| arabidopsis rpp4 is a member of the rpp5 multigene family of tir-nb-lrr genes and confers downy mildew resistance through multiple signalling components. | in arabidopsis, rpp4 confers resistance to peronospora parasitica (p.p.) races emoy2 and emwa1 (downy mildew). we identified rpp4 in col-0 as a member of the clustered rpp5 multigene family encoding nucleotide-binding leucine-rich repeat proteins with toll/interleukin-1 receptor domains. rpp4 is the orthologue of rpp5 which, in addition to recognizing p.p. race noco2, also mediates resistance to emoy2 and emwa1. most differences between rpp4 and rpp5 occur in residues that constitute the tir dom ... | 2002 | 11846877 |
| differential effectiveness of salicylate-dependent and jasmonate/ethylene-dependent induced resistance in arabidopsis. | salicylic acid (sa), jasmonic acid (ja), and ethylene (et) are each involved in the regulation of basal resistance against different pathogens. these three signals play important roles in induced resistance as well. sa is a key regulator of pathogen-induced systemic acquired resistance (sar), whereas ja and et are required for rhizobacteria-mediated induced systemic resistance (isr). both types of induced resistance are effective against a broad spectrum of pathogens. in this study, we compared ... | 2002 | 11858171 |
| esa1, an arabidopsis mutant with enhanced susceptibility to a range of necrotrophic fungal pathogens, shows a distorted induction of defense responses by reactive oxygen generating compounds. | an arabidopsis thaliana mutant, esa1, that shows enhanced susceptibility to the necrotrophic pathogens alternaria brassicicola, botrytis cinerea and plectosphaerella cucumerina, but has wild-type levels of resistance to the biotrophic pathogens pseudomonas syringae pv. tomato and peronospora parasitica. the enhanced susceptibility towards necrotrophic pathogens correlated with a delayed induction of phytoalexin accumulation and delayed induction of the plant defensin gene pdf1.2 upon inoculation ... | 2002 | 11862946 |
| rin4 interacts with pseudomonas syringae type iii effector molecules and is required for rpm1-mediated resistance in arabidopsis. | in arabidopsis, rpm1 confers resistance against pseudomonas syringae expressing either of two sequence unrelated type iii effectors, avrrpm1 or avrb. an rpm1-interacting protein (rin4) coimmunoprecipitates from plant cell extracts with avrb, avrrpm1, or rpm1. reduction of rin4 protein levels inhibits both the hypersensitive response and the restriction of pathogen growth controlled by rpm1. rin4 reduction causes diminution of rpm1. rin4 reduction results in heightened resistance to virulent pero ... | 2002 | 11955429 |
| isolation and characterization of broad-spectrum disease-resistant arabidopsis mutants. | to identify arabidopsis mutants that constitutively express systemic acquired resistance (sar), we constructed reporter lines expressing the firefly luciferase gene under the control of the sar-inducible pr-1 promoter (pr-1/luc). after ems mutagenesis of a well-characterized transgenic line, we screened 250,000 m(2) plants for constitutive expression of the reporter gene in vivo. from a mutant collection containing several hundred putative mutants, we concentrated on 16 mutants lacking spontaneo ... | 2002 | 11973319 |
| the arabidopsis hrl1 mutation reveals novel overlapping roles for salicylic acid, jasmonic acid and ethylene signalling in cell death and defence against pathogens. | defence against pathogens in arabidopsis is orchestrated by at least three signalling molecules: salicylic acid (sa), jasmonic acid (ja) and ethylene (et). the hrl1 (hypersensitive response-like lesions 1) mutant of arabidopsis is characterized by spontaneous necrotic lesions, accumulation of reactive oxygen species, constitutive expression of sa- and et/ja-responsive defence genes, and enhanced resistance to virulent bacterial and oomycete pathogens. epistasis analyses of hrl1 with npr1, etr1, ... | 2002 | 12028576 |
| arabidopsis sgt1b is required for defense signaling conferred by several downy mildew resistance genes. | we describe the identification of a mutant in the arabidopsis accession columbia (col-0) that exhibits enhanced downy mildew (edm1) susceptibility to several peronospora parasitica isolates, including the rpp7-diagnostic isolate hiks1. the mutation was mapped to chromosome iv and characterized physically as a 35-kb deletion spanning seven genes. one of these genes complemented the mutant to full wild-type resistance against all of the peronospora isolates tested. this gene (atsgt1b) encodes a pr ... | 2002 | 12034892 |
| characterization of a novel, defense-related arabidopsis mutant, cir1, isolated by luciferase imaging. | in order to identify components of the defense signaling network engaged following attempted pathogen invasion, we generated a novel pr-1::luciferase (luc) transgenic line that was deployed in an imaging-based screen to uncover defense-related mutants. the recessive mutant designated cir1 exhibited constitutive expression of salicylic acid (sa), jasmonic acid (ja)/ethylene, and reactive oxygen intermediate-dependent genes. moreover, this mutation conferred resistance against the bacterial pathog ... | 2002 | 12059104 |
| nhl25 and nhl3, two ndr1/hin1-1ike genes in arabidopsis thaliana with potential role(s) in plant defense. | the arabidopsis genome contains 28 genes with sequence homology to the arabidopsis ndr1 gene and the tobacco hin1 gene. expression analysis of eight of these genes identified two (nhl25 and nhl3 for ndr1/hin1-like) that show pathogen-dependent mrna accumulation. transcripts did not accumulate during infection with virulent pseudomonas syringae pv. tomato dc3000 but did accumulate specifically when the bacteria carried any of the four avirulence genes avrrpm1, avrrpt2, avrb, or avrrps4. furthermo ... | 2002 | 12059109 |
| role of salicylic acid and nim1/npr1 in race-specific resistance in arabidopsis. | salicylic acid (sa) and the nim1/npr1 protein have both been demonstrated to be required for systemic acquired resistance (sar) and implicated in expression of race-specific resistance. in this work, we analyzed the role that each of these molecules play in the resistance response triggered by members of two subclasses of resistance (r) genes, members of which recognize unrelated pathogens. we tested the ability of tir and coiled-coil-class (also known as leucine-zipper-class) r genes to confer ... | 2002 | 12072475 |
| probing the diversity of the arabidopsis glutathione s-transferase gene family. | glutathione s-transferases (gsts) appear to be ubiquitous in plants and have defined roles in herbicide detoxification. in contrast, little is known about their roles in normal plant physiology and during responses to biotic and abiotic stress. forty-seven members of the gst super-family were identified in the arabidopsis genome, grouped into four classes, with amino acid sequence identity between classes being below 25%. the two small zeta (gstz) and theta (gstt) classes have related gsts in an ... | 2002 | 12090627 |
| arabidopsis son1 is an f-box protein that regulates a novel induced defense response independent of both salicylic acid and systemic acquired resistance. | one of several induced defense responses in plants is systemic acquired resistance (sar), which is regulated by salicylic acid and in arabidopsis by the nim1/npr1 protein. to identify additional components of the sar pathway or other genes that regulate sar-independent resistance, we performed genetic suppressor screens of mutagenized nim1-1 seedlings, which are highly susceptible to infection by peronospora parasitica. we isolated the son1 (suppressor of nim1-1) mutant, which shows full restora ... | 2002 | 12119368 |
| production of salicylic acid precursors is a major function of phenylalanine ammonia-lyase in the resistance of arabidopsis to peronospora parasitica. | arabidopsis ecotype columbia (col-0) seedlings, transformed with a phenylalanine ammonia-lyase 1 promoter (pal1)-[beta]-glucuronidase (gus) reporter construct, were inoculated with virulent and avirulent isolates of peronospora parasitica. the pal1 promoter was constitutively active in the light in vascular tissue but was induced only in the vicinity of fungal structures in the incompatible interaction. a double-staining procedure was developed to distinguish between gus activity and fungal stru ... | 1996 | 12239383 |
| a putative lipid transfer protein involved in systemic resistance signalling in arabidopsis. | localized attack by a necrotizing pathogen induces systemic acquired resistance (sar) to subsequent attack by a broad range of normally virulent pathogens. salicylic acid accumulation is required for activation of local defenses, such as pathogenesis-related protein accumulation, at the initial site of attack, and for subsequent expression of sar upon secondary, distant challenge. although salicylic acid moves through the plant, it is apparently not an essential mobile signal. we screened agroba ... | 2002 | 12353036 |
| over-expression of tga5, which encodes a bzip transcription factor that interacts with nim1/npr1, confers sar-independent resistance in arabidopsis thaliana to peronospora parasitica. | the arabidopsis thaliana nim1/npr1 gene product is required for induction of systemic acquired resistance (sar) by pathogens, salicylic acid (sa) or synthetic sa analogs. we identified, in a yeast two-hybrid screen, two nim1/npr1 interacting proteins, tga2 and tga5, which belong to the basic region, leucine zipper (bzip) family of transcription factors. both tga2 and tga5 strongly interact with nim1/npr1 in yeast and in vitro, and recognize the as-1 cis element found within the promoter of sever ... | 2002 | 12383081 |
| rcy1, an arabidopsis thaliana rpp8/hrt family resistance gene, conferring resistance to cucumber mosaic virus requires salicylic acid, ethylene and a novel signal transduction mechanism. | the dominant locus, rcy1, in the arabidopsis thaliana ecotype c24 confers resistance to the yellow strain of cucumber mosaic virus (cmv-y). the rcy1 locus was mapped to a 150-kb region on chromosome 5. sequence comparison of this region from c24 and a cmv-y-susceptible c24 mutant predicts that the rcy1 gene encodes a 104-kda cc-nbs-lrr-type protein. the rcy1 gene from c24, when expressed in the susceptible ecotype wassilewskija (ws), restricted the systemic spread of virus. rcy1 is allelic to th ... | 2002 | 12472683 |
| a genetic interval and physical contig spanning the peronospora parasitica (at) avirulence gene locus atr1nd. | in peronospora parasitica (at) (downy mildew), the genetic determinants of cultivar-specific recognition by arabidopsis thaliana are the arabidopsis thaliana-recognised (atr) avirulence genes. we describe the identification of 10 amplified fragment length polymorphism (aflp) markers that define a genetic mapping interval for the atr1nd avirulence allele, the presence of which is perceived by the rpp1nd resistance gene. furthermore, we have constructed a p. parasitica (at) bacterial artificial ch ... | 2003 | 12553934 |
| gfp-tagging of cell components reveals the dynamics of subcellular re-organization in response to infection of arabidopsis by oomycete pathogens. | cytoplasmic aggregation, the rapid translocation of cytoplasm and subcellular components to the site of pathogen penetration, is one of the earliest reactions of plant cells against attack by microorganisms. we have investigated cytoplasmic aggregation during arabidopsis-oomycete interactions. infection by non-pathogenic phytophthora sojae was prevented in the plant epidermal cell layer, whereas peronospora parasitica isolates cala2 (avirulent) and noks1 (virulent) could both penetrate into the ... | 2003 | 12609049 |
| members of the arabidopsis wrky group iii transcription factors are part of different plant defense signaling pathways. | wrky proteins are a large group of transcription factors restricted to the plant kingdom. in arabidopsis thaliana, the gene family consists of 74 members. here, we analyzed the expression of all 13 members of one main wrky subgroup and found that the majority are responsive both to pathogen infection and to salicylic acid. temporal expression studies during compatible, incompatible, and nonhost interactions and employing plant defense-signaling mutants allowed us to define four distinct wrky sub ... | 2003 | 12744458 |
| the expression of the t-snare atsnap33 is induced by pathogens and mechanical stimulation. | the fusion of vesicles in the secretory pathway involves the interaction of t-soluble n-ethylmaleimide-sensitive factor attachment protein receptors (t-snares) on the target membrane and v-snares on the vesicle membrane. atsnap33 is an arabidopsis homolog of the neuronal t-snare snap-25 involved in exocytosis and is localized at the cell plate and at the plasma membrane. in this paper, the expression of atsnap33 was analyzed after different biotic and abiotic stresses. the expression of atsnap33 ... | 2003 | 12746539 |
| pathogen-induced systemic plant signal triggers dna rearrangements. | plant genome stability is known to be affected by various abiotic environmental conditions, but little is known about the effect of pathogens. for example, exposure of maize plants to barley stripe mosaic virus seems to activate transposable elements and to cause mutations in the non-infected progeny of infected plants. the induction by barley stripe mosaic virus of an inherited effect may mean that the virus has a non-cell-autonomous influence on genome stability. infection with peronospora par ... | 2003 | 12802336 |
| ethylene and jasmonic acid signaling affect the npr1-independent expression of defense genes without impacting resistance to pseudomonas syringae and peronospora parasitica in the arabidopsis ssi1 mutant. | salicylic acid (sa), ethylene, and jasmonic acid (ja) are important signaling molecules in plant defense to biotic stress. an intricate signaling network involving sa, ethylene, and ja fine tunes plant defense responses. sa-dependent defense responses in arabidopsis thaliana are mediated through npr1-dependent and -independent mechanisms. we have previously shown that activation of an npr1-independent defense mechanism confers enhanced disease resistance and constitutive expression of the pathog ... | 2003 | 12848424 |
| targeted activation tagging of the arabidopsis nbs-lrr gene, adr1, conveys resistance to virulent pathogens. | a transgenic arabidopsis line containing a chimeric pr-1::luciferase (luc) reporter gene was subjected to mutagenesis with activation tags. screening of lines via high-throughput luc imaging identified a number of dominant arabidopsis mutants that exhibited enhanced pr-1 gene expression. here, we report the characterization of one of these mutants, designated activated disease resistance (adr) 1. this line showed constitutive expression of a number of key defense marker genes and accumulated sal ... | 2003 | 12906111 |
| a developmental response to pathogen infection in arabidopsis. | we present evidence that susceptible arabidopsis plants accelerate their reproductive development and alter their shoot architecture in response to three different pathogen species. we infected 2-week-old arabidopsis seedlings with two bacterial pathogens, pseudomonas syringae and xanthomonas campestris, and an oomycete, peronospora parasitica. infection with each of the three pathogens reduced time to flowering and the number of aerial branches on the primary inflorescence. in the absence of co ... | 2003 | 12970499 |
| organ-specificity in a plant disease is determined independently of r gene signaling. | the molecular basis of organ specificity in plant diseases is little characterized. downy mildew of arabidopsis caused by the oomycete hyaloperonospora parasitica (formerly peronospora parasitica) is characteristically a leaf disease. resistant host genotypes recognize the pathogen in a gene-for-gene dependent manner and respond with the production of h2o2 and the execution of a genetically programmed hypersensitive cell death (hr). we inoculated the roots of arabidopsis genotypes col-0, ws-0, a ... | 2003 | 12971598 |
| the botrytis susceptible1 gene encodes an r2r3myb transcription factor protein that is required for biotic and abiotic stress responses in arabidopsis. | the molecular and cellular mechanisms involved in plant resistance to the necrotrophic fungal pathogen botrytis cinerea and their genetic control are poorly understood. botrytis causes severe disease in a wide range of plant species, both in the field and in postharvest situations, resulting in significant economic losses. we have isolated the bos1 (botrytis-susceptible1) gene of arabidopsis based on a t-dna insertion allele that resulted in increased susceptibility to botrytis infection. the bo ... | 2003 | 14555693 |
| an arabidopsis callose synthase, gsl5, is required for wound and papillary callose formation. | arabidopsis was transformed with double-stranded rna interference (dsrnai) constructs designed to silence three putative callose synthase genes: glucan synthase-like5 (gsl5), gsl6, and gsl11. both wound callose and papillary callose were absent in lines transformed with gsl5 dsrnai and in a corresponding sequence-indexed gsl5 t-dna insertion line but were unaffected in gsl6 and gsl11 dsrnai lines. these data provide strong genetic evidence that the gsl genes of higher plants encode proteins that ... | 2003 | 14555698 |
| induced systemic resistance in arabidopsis thaliana in response to root inoculation with pseudomonas fluorescens cha0. | root inoculation of arabidopsis thaliana ecotype columbia with pseudomonas fluorescens cha0r partially protected leaves from the oomycete peronospora parasitica. the molecular determinants of pseudomonas fluorescens cha0r for this induced systemic resistance (isr) were investigated, using mutants derived from strain cha0: cha400 (pyoverdine deficient), cha805 (exoprotease deficient), cha77 (hcn deficient), cha660 (pyoluteorin deficient), cha631 (2,4-diacetylphloroglucinol [dapg] deficient), and ... | 2003 | 14558686 |
| knockout analysis of arabidopsis transcription factors tga2, tga5, and tga6 reveals their redundant and essential roles in systemic acquired resistance. | arabidopsis nonexpresser of pathogenesis-related (pr) genes (npr1) is the sole positive regulator that has been shown to be essential for the induction of systemic acquired resistance. in npr1 mutant plants, salicylic acid (sa)-mediated pr gene expression and pathogen resistance are abolished completely. npr1 has been shown to interact with three closely related tga transcription factors-tga2, tga5, and tga6-in yeast two-hybrid assays. to elucidate the biological functions of these three tga tra ... | 2003 | 14576289 |
| a gain-of-function mutation in a plant disease resistance gene leads to constitutive activation of downstream signal transduction pathways in suppressor of npr1-1, constitutive 1. | plants have evolved sophisticated defense mechanisms against pathogen infections, during which resistance (r) genes play central roles in recognizing pathogens and initiating defense cascades. most of the cloned r genes share two common domains: the central domain, which encodes a nucleotide binding adaptor shared by apaf-1, certain r proteins, and ced-4 (nb-arc), plus a c-terminal region that encodes leu-rich repeats (lrr). in arabidopsis, a dominant mutant, suppressor of npr1-1, constitutive 1 ... | 2003 | 14576290 |
| the pseudomonas syringae type iii effector avrrpt2 functions downstream or independently of sa to promote virulence on arabidopsis thaliana. | avrrpt2, a pseudomonas syringae type iii effector protein, functions from inside plant cells to promote the virulence of p. syringae pv. tomato strain dc3000 (pstdc3000) on arabidopsis thaliana plants lacking a functional copy of the corresponding rps2 resistance gene. in this study, we extended our understanding of avrrpt2 virulence activity by exploring the hypothesis that avrrpt2 promotes pstdc3000 virulence by suppressing plant defenses. when delivered by pstdc3000, avrrpt2 suppresses pathog ... | 2004 | 14756766 |
| internal transcribed spacer 2 amplicon as a molecular marker for identification of peronospora parasitica (crucifer downy mildew). | the purpose of the study was to characterize the internal transcribed spacer (its) regions of peronospora parasitica (crucifer downy mildew) in order to evaluate their potential as molecular markers for pathogen identification. | 2004 | 14962138 |
| oxi1 kinase is necessary for oxidative burst-mediated signalling in arabidopsis. | active oxygen species (aos) generated in response to stimuli and during development can function as signalling molecules in eukaryotes, leading to specific downstream responses. in plants these include such diverse processes as coping with stress (for example pathogen attack, wounding and oxygen deprivation), abscisic-acid-induced guard-cell closure, and cellular development (for example root hair growth). despite the importance of signalling via aos in eukaryotes, little is known about the prot ... | 2004 | 14985766 |
| diversity of the hyaloperonospora parasitica complex from core brassicaceous hosts based on its rdna sequences. | sequence analysis of the its region of rdna was used to investigate the level of genetic diversity occurring within hyaloperonospora parasiticia, and to show the relationship between phylogenies of these fungi and their hosts (brassicaceae). maximum parsimony and neighbour-joining analyses were performed using sequences from 32 isolates of hyaloperonospora and perofascia, which infect core brassicaceous hosts. for comparison, five isolates of peronospora were also studied. the constructed phylog ... | 2003 | 15000233 |
| silencing of the mitogen-activated protein kinase mpk6 compromises disease resistance in arabidopsis. | here, we use a loss-of-function approach to demonstrate that the arabidopsis (arabidopsis thaliana) mitogen-activated protein kinase (mapk) mpk6 plays a role in resistance to certain pathogens. mpk6-silenced arabidopsis showed no apparent morphological phenotype or reduced fertility, indicating mpk6 is not required for development. however, resistances to an avirulent strain of peronospora parasitica and avirulent and virulent strains of pseudomonas syringae were compromised, suggesting that mpk ... | 2004 | 15020743 |
| the timing of senescence and response to pathogens is altered in the ascorbate-deficient arabidopsis mutant vitamin c-1. | the ozone-sensitive arabidopsis mutant vitamin c-1 (vtc1) is deficient in l-ascorbic acid (asa) due to a mutation in gdp-man pyrophosphorylase (conklin et al., 1999), an enzyme involved in the asa biosynthetic pathway (smirnoff et al., 2001). in this study, the physiology of this asa deficiency was initially investigated in response to biotic (virulent pathogens) stress and subsequently with regards to the onset of senescence. infection with either virulent pseudomonas syringae or peronospora pa ... | 2004 | 15064386 |
| the maintenance of extreme amino acid diversity at the disease resistance gene, rpp13, in arabidopsis thaliana. | we have used the naturally occurring plant-parasite system of arabidopsis thaliana and its common parasite peronospora parasitica (downy mildew) to study the evolution of resistance specificity in the host population. dna sequence of the resistance gene, rpp13, from 24 accessions, including 20 from the united kingdom, revealed amino acid sequence diversity higher than that of any protein coding gene reported so far in a. thaliana. a significant excess of amino acid polymorphism segregating withi ... | 2004 | 15082565 |
| a novel cost of r gene resistance in the presence of disease. | resistance responses can impose fitness costs when pests are absent. here, we test whether the induction of resistance can decrease fitness even in plants under attack; we call this potential outcome a net cost with attack. using lines in which genetic background was controlled, we investigated whether susceptible arabidopsis thaliana plants can outperform r gene resistant plants when infected with pathogens. for the r gene rps2, there was a fitness benefit of resistance in the presence of intra ... | 2004 | 15122498 |
| arabidopsis downy mildew resistance gene rpp27 encodes a receptor-like protein similar to clavata2 and tomato cf-9. | the arabidopsis ler-rpp27 gene confers atsgt1b-independent resistance to downy mildew (peronospora parasitica) isolate hiks1. the rpp27 locus was mapped to a four-bacterial artificial chromosome interval on chromosome 1 from genetic analysis of a cross between the enhanced susceptibility mutant col-edm1 (col-sgt1) and landsberg erecta (ler-0). a cf-like candidate gene in this interval was pcr amplified from ler-0 and transformed into mutant col-rpp7.1 plants. homozygous transgenic lines conferre ... | 2004 | 15155873 |
| two tir:nb:lrr genes are required to specify resistance to peronospora parasitica isolate cala2 in arabidopsis. | resistance responses that plants deploy in defence against pathogens are often triggered following a recognition event mediated by resistance (r) genes. the encoded r proteins usually contain a nucleotide-binding site (nb) and a leucine-rich repeat (lrr) domain. they are further classified into those that contain an n-terminal coiled coil (cc) motif or a toll interleukin receptor (tir) domain. such r genes, when transferred into a susceptible plant of the same or closely related species, usually ... | 2004 | 15165183 |
| gene expression signatures from three genetically separable resistance gene signaling pathways for downy mildew resistance. | resistance gene-dependent disease resistance to pathogenic microorganisms is mediated by genetically separable regulatory pathways. using the genechip arabidopsis genome array, we compared the expression profiles of approximately 8,000 arabidopsis genes following activation of three rpp genes directed against the pathogenic oomycete peronospora parasitica. judicious choice of p. parasitica isolates and loss of resistance plant mutants allowed us to compare the responses controlled by three genet ... | 2004 | 15181204 |
| a key role for ald1 in activation of local and systemic defenses in arabidopsis. | the arabidopsis thaliana agd2-like defense response protein1 (ald1) mutant was previously found to be hypersusceptible to the virulent bacterial pathogen pseudomonas syringae and had reduced accumulation of the defense signal salicylic acid (sa). ald1 was shown to possess aminotransferase activity in vitro, suggesting it generates an amino acid-derived defense signal. we now find ald1 to be a key defense component that acts in multiple contexts and partially requires the phytoalexin deficient4 ( ... | 2004 | 15447647 |
| the bos loci of arabidopsis are required for resistance to botrytis cinerea infection. | three botrytis-susceptible mutants bos2, bos3, and bos4 which define independent and novel genetic loci required for arabidopsis resistance to botrytis cinerea were isolated. the bos2 mutant is susceptible to b. cinerea but retains wild-type levels of resistance to other pathogens tested, indicative of a defect in a response pathway more specific to b. cinerea. the bos3 and bos4 mutants also show increased susceptibility to alternaria brassicicola, another necrotrophic pathogen, suggesting a bro ... | 2004 | 15500471 |