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5200.9453NHL25 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. Furthermore, expression of avrRpt2 in plants containing the corresponding resistance gene, RPS2, was sufficient to induce transcript accumulation. However, during infection with an avirulent oomycete, Peronospora parasitica isolate Cala-2, only NHL25 expression was reproducibly induced. Salicylic acid (SA) treatment can induce expression of NHL25 and NHL3. Studies performed on nahG plants showed that, during interaction with avirulent bacteria, only the expression of NHL25 but not that of NHL3 was affected. This suggests involvement of separate SA-dependent and SA-independent pathways, respectively, in the transcriptional activation of these genes. Bacteria-induced gene expression was not abolished in ethylene- (etrl-3 and ein2-1) and jasmonate- (coil-1) insensitive mutants or in mutants impaired in disease resistance (ndr1-1 and pad4-1). Interestingly, NHL3 transcripts accumulated after infiltration with the avirulent hrcC mutant of Pseudomonas syringae pv. tomato DC3000 and nonhost bacteria but not with the virulent Pseudomonas syringae pv. tomato DC3000, suggesting that virulent bacteria may suppress NHL3 expression during pathogenesis. Hence, the expression patterns and sequence homology to NDR1 and HIN1 suggest one or more potential roles for these genes in plant resistance.200212059109
10010.9436Pto3 and Pto4: novel genes from Lycopersicon hirsutum var. glabratum that confer resistance to Pseudomonas syringae pv tomato. Accessions of wild Lycopersicon germplasm were screened for resistance to Pseudomonas syringae pv tomato (P.s. tomato). Resistance to both race-0 and race-1 strains of P.s. tomato was identified in L. pimpinellifolium, L. peruvianum and L. hirsutum var. glabratum. Resistance to race-0 derived from L. hirsutum var. glabratum (Pto3) appeared to be inherited independently of Pto1 and Pto2. Filial and backcross generations derived from interspecific crosses between L. esculentum and L. hirsutum var. glabratum revealed that Pto3 resistance was inherited in a complex fashion and was incompletely dominant under conditions of high bacteria inocula. Resistance to P.s. tomato race-1 (Pto4) was also identified in L. hirsutum var. glabratum. Pto3 and Pto4 segregated independently of each other.199424178099
4820.9432Priming of the Arabidopsis pattern-triggered immunity response upon infection by necrotrophic Pectobacterium carotovorum bacteria. Boosted responsiveness of plant cells to stress at the onset of pathogen- or chemically induced resistance is called priming. The chemical β-aminobutyric acid (BABA) enhances Arabidopsis thaliana resistance to hemibiotrophic bacteria through the priming of the salicylic acid (SA) defence response. Whether BABA increases Arabidopsis resistance to the necrotrophic bacterium Pectobacterium carotovorum ssp. carotovorum (Pcc) is not clear. In this work, we show that treatment with BABA protects Arabidopsis against the soft-rot pathogen Pcc. BABA did not prime the expression of the jasmonate/ethylene-responsive gene PLANT DEFENSIN 1.2 (PDF1.2), the up-regulation of which is usually associated with resistance to necrotrophic pathogens. Expression of the SA marker gene PATHOGENESIS RELATED 1 (PR1) on Pcc infection was primed by BABA treatment, but SA-defective mutants demonstrated a wild-type level of BABA-induced resistance against Pcc. BABA primed the expression of the pattern-triggered immunity (PTI)-responsive genes FLG22-INDUCED RECEPTOR-LIKE KINASE 1 (FRK1), ARABIDOPSIS NON-RACE SPECIFIC DISEASE RESISTANCE GENE (NDR1)/HAIRPIN-INDUCED GENE (HIN1)-LIKE 10 (NHL10) and CYTOCHROME P450, FAMILY 81 (CYP81F2) after inoculation with Pcc or after treatment with purified bacterial microbe-associated molecular patterns, such as flg22 or elf26. PTI-mediated callose deposition was also potentiated in BABA-treated Arabidopsis, and BABA boosted Arabidopsis stomatal immunity to Pcc. BABA treatment primed the PTI response in the SA-defective mutants SA induction deficient 2-1 (sid2-1) and phytoalexin deficient 4-1 (pad4-1). In addition, BABA priming was associated with open chromatin configurations in the promoter region of PTI marker genes. Our data indicate that BABA primes the PTI response upon necrotrophic bacterial infection and suggest a role for the PTI response in BABA-induced resistance.201322947164
6630.9429Isolation of new Arabidopsis mutants with enhanced disease susceptibility to Pseudomonas syringae by direct screening. To identify plant defense components that are important in restricting the growth of virulent pathogens, we screened for Arabidopsis mutants in the accession Columbia (carrying the transgene BGL2-GUS) that display enhanced disease susceptibility to the virulent bacterial pathogen Pseudomonas syringae pv. maculicola (Psm) ES4326. Among six (out of a total of 11 isolated) enhanced disease susceptibility (eds) mutants that were studied in detail, we identified one allele of the previously described npr1/nim1/sai1 mutation, which is affected in mounting a systemic acquired resistance response, one allele of the previously identified EDS5 gene, and four EDS genes that have not been previously described. The six eds mutants studied in detail (npr1-4, eds5-2, eds10-1, eds11-1, eds12-1, and eds13-1) displayed different patterns of enhanced susceptibility to a variety of phytopathogenic bacteria and to the obligate biotrophic fungal pathogen Erysiphe orontii, suggesting that particular EDS genes have pathogen-specific roles in conferring resistance. All six eds mutants retained the ability to mount a hypersensitive response and to restrict the growth of the avirulent strain Psm ES4326/avrRpt2. With the exception of npr1-4, the mutants were able to initiate a systemic acquired resistance (SAR) response, although enhanced growth of Psm ES4326 was still detectable in leaves of SAR-induced plants. The data presented here indicate that eds genes define a variety of components involved in limiting pathogen growth, that many additional EDS genes remain to be discovered, and that direct screens for mutants with altered susceptibility to pathogens are helpful in the dissection of complex pathogen response pathways in plants.19989611172
4740.9414LTP3 contributes to disease susceptibility in Arabidopsis by enhancing abscisic acid (ABA) biosynthesis. Several plant lipid transfer proteins (LTPs) act positively in plant disease resistance. Here, we show that LTP3 (At5g59320), a pathogen and abscisic acid (ABA)-induced gene, negatively regulates plant immunity in Arabidopsis. The overexpression of LTP3 (LTP3-OX) led to an enhanced susceptibility to virulent bacteria and compromised resistance to avirulent bacteria. On infection of LTP3-OX plants with Pseudomonas syringae pv. tomato, genes involved in ABA biosynthesis, NCED3 and AAO3, were highly induced, whereas salicylic acid (SA)-related genes, ICS1 and PR1, were down-regulated. Accordingly, in LTP3-OX plants, we observed increased ABA levels and decreased SA levels relative to the wild-type. We also showed that the LTP3 overexpression-mediated enhanced susceptibility was partially dependent on AAO3. Interestingly, loss of function of LTP3 (ltp3-1) did not affect ABA pathways, but resulted in PR1 gene induction and elevated SA levels, suggesting that LTP3 can negatively regulate SA in an ABA-independent manner. However, a double mutant consisting of ltp3-1 and silent LTP4 (ltp3/ltp4) showed reduced susceptibility to Pseudomonas and down-regulation of ABA biosynthesis genes, suggesting that LTP3 acts in a redundant manner with its closest homologue LTP4 by modulating the ABA pathway. Taken together, our data show that LTP3 is a novel negative regulator of plant immunity which acts through the manipulation of the ABA-SA balance.201626123657
4250.9412Suppression of the rice fatty-acid desaturase gene OsSSI2 enhances resistance to blast and leaf blight diseases in rice. Fatty acids and their derivatives play important signaling roles in plant defense responses. It has been shown that suppressing a gene for stearoyl acyl carrier protein fatty-acid desaturase (SACPD) enhances the resistance of Arabidopsis (SSI2) and soybean to multiple pathogens. In this study, we present functional analyses of a rice homolog of SSI2 (OsSSI2) in disease resistance of rice plants. A transposon insertion mutation (Osssi2-Tos17) and RNAi-mediated knockdown of OsSSI2 (OsSSI2-kd) reduced the oleic acid (18:1) level and increased that of stearic acid (18:0), indicating that OsSSI2 is responsible for fatty-acid desaturase activity. These plants displayed spontaneous lesion formation in leaf blades, retarded growth, slight increase in endogenous free salicylic acid (SA) levels, and SA/benzothiadiazole (BTH)-specific inducible genes, including WRKY45, a key regulator of SA/BTH-induced resistance, in rice. Moreover, the OsSSI2-kd plants showed markedly enhanced resistance to the blast fungus Magnaporthe grisea and leaf-blight bacteria Xanthomonas oryzae pv. oryzae. These results suggest that OsSSI2 is involved in the negative regulation of defense responses in rice, as are its Arabidopsis and soybean counterparts. Microarray analyses identified 406 genes that were differentially expressed (>or=2-fold) in OsSSI2-kd rice plants compared with wild-type rice and, of these, approximately 39% were BTH responsive. Taken together, our results suggest that induction of SA-responsive genes, including WRKY45, is likely responsible for enhanced disease resistance in OsSSI2-kd rice plants.200919522564
4560.9412Vitis vinifera VvNPR1.1 is the functional ortholog of AtNPR1 and its overexpression in grapevine triggers constitutive activation of PR genes and enhanced resistance to powdery mildew. Studying grapevine (Vitis vinifera) innate defense mechanisms is a prerequisite to the development of new protection strategies, based on the stimulation of plant signaling pathways to trigger pathogen resistance. Two transcriptional coactivators (VvNPR1.1 and VvNPR1.2) with similarity to Arabidopsis thaliana NPR1 (Non-Expressor of PR genes 1), a well-characterized and key signaling element of the salicylic acid (SA) pathway, were recently isolated in Vitis vinifera. In this study, functional characterization of VvNPR1.1 and VvNPR1.2, including complementation of the Arabidopsis npr1 mutant, revealed that VvNPR1.1 is a functional ortholog of AtNPR1, whereas VvNPR1.2 likely has a different function. Ectopic overexpression of VvNPR1.1 in the Arabidopsis npr1-2 mutant restored plant growth at a high SA concentration, Pathogenesis Related 1 (PR1) gene expression after treatment with SA or bacterial inoculation, and resistance to virulent Pseudomonas syringae pv. maculicola bacteria. Moreover, stable overexpression of VvNPR1.1-GFP in V. vinifera resulted in constitutive nuclear localization of the fusion protein and enhanced PR gene expression in uninfected plants. Furthermore, grapevine plants overexpressing VvNPR1.1-GFP exhibited an enhanced resistance to powdery mildew infection. This work highlights the importance of the conserved SA/NPR1 signaling pathway for resistance to biotrophic pathogens in V. vinifera.201121505863
5770.9409Functional analysis of NtMPK2 uncovers its positive role in response to Pseudomonas syringae pv. tomato DC3000 in tobacco. Mitogen-activated protein kinase cascades are highly conserved signaling modules downstream of receptors/sensors and play pivotal roles in signaling plant defense against pathogen attack. Extensive studies on Arabidopsis MPK4 have implicated that the MAP kinase is involved in multilayered plant defense pathways. In this study, we identified tobacco NtMPK2 as an ortholog of AtMPK4. Transgenic tobacco overexpressing NtMPK2 markedly enhances resistance to Pseudomonas syringae pv. tomato DC3000 (Pst DC3000) virulent and avirulent strains. Transcriptome analysis of NtMPK2-dependent genes shows that possibly the basal resistance system is activated by NtMPK2 overexpression. In addition to NtMPK2-mediated resistance, multiple pathways are involved in response to the avirulent bacteria based on analysis of Pst-responding genes, including SA and ET pathways. Notably, it is possible that biosynthesis of antibacterial compounds is responsible for inhibition of Pst DC3000 avirulent strain when programmed cell death processes in the host. Our results uncover that NtMPK2 positively regulate tobacco defense response to Pst DC3000 and improve our understanding of plant molecular defense mechanism.201626482478
9280.9406Quantitative trait loci for partial resistance to Pseudomonas syringae pv. maculicola in Arabidopsis thaliana. Segregation of partial resistance to Pseudomonas syringae pv. maculicola (Psm) ES4326 was studied in the recombinant inbred population created from accessions (ecotypes) Columbia (Col-4), the more susceptible parent, and Landsberg (Ler-0). Plants were spray inoculated with lux-transformed bacteria in experiments to measure susceptibility. The amount of disease produced on a range of Col × Ler lines by spray inoculation was highly correlated with that produced by pressure infiltration of bacteria into the apoplast. Quantitative trait locus (QTL) analysis identified four loci that contributed to partial resistance: QRpsJIC-1.1, QRpsJIC-2.1, QRpsJIC-3.1 and QRpsJIC-5.1 on chromosomes 1, 2, 3 and 5, respectively. QRpsJIC-3.1, located 8.45 cM from the top of the consensus genetic map of chromosome 3, had a large, approximately additive effect on partial resistance, explaining 50% of the genetic variation in this population. Fine mapping narrowed the region within which this QTL was located to 62 genes. A list of candidate genes included several major classes of resistance gene.201323724899
1090.9406YODA Kinase Controls a Novel Immune Pathway of Tomato Conferring Enhanced Disease Resistance to the Bacterium Pseudomonas syringae. Mitogen-activated protein kinases (MAPK) play pivotal roles in transducing developmental cues and environmental signals into cellular responses through pathways initiated by MAPK kinase kinases (MAP3K). AtYODA is a MAP3K of Arabidopsis thaliana that controls stomatal development and non-canonical immune responses. Arabidopsis plants overexpressing a constitutively active YODA protein (AtCA-YDA) show broad-spectrum disease resistance and constitutive expression of defensive genes. We tested YDA function in crops immunity by heterologously overexpressing AtCA-YDA in Solanum lycopersicum. We found that these tomato AtCA-YDA plants do not show developmental phenotypes and fitness alterations, except a reduction in stomatal index, as reported in Arabidopsis AtCA-YDA plants. Notably, AtCA-YDA tomato plants show enhanced resistance to the bacterial pathogen Pseudomonas syringae pv. tomato DC3000 and constitutive upregulation of defense-associated genes, corroborating the functionality of YDA in tomato immunity. This function was further supported by generating CRISPR/Cas9-edited tomato mutants impaired in the closest orthologs of AtYDA [Solyc08g081210 (SlYDA1) and Solyc03g025360 (SlYDA2)]. Slyda1 and Slyda2 mutants are highly susceptible to P. syringae pv. tomato DC3000 in comparison to wild-type plants but only Slyda2 shows altered stomatal index. These results indicate that tomato orthologs have specialized functions and support that YDA also regulates immune responses in tomato and may be a trait for breeding disease resistance.202033154763
39100.9406Rutin-Mediated Priming of Plant Resistance to Three Bacterial Pathogens Initiating the Early SA Signal Pathway. Flavonoids are ubiquitous in the plant kingdom and have many diverse functions, including UV protection, auxin transport inhibition, allelopathy, flower coloring and insect resistance. Here we show that rutin, a proud member of the flavonoid family, could be functional as an activator to improve plant disease resistances. Three plant species pretreated with 2 mM rutin were found to enhance resistance to Xanthomonas oryzae pv. oryzae, Ralstonia solanacearum, and Pseudomonas syringae pv. tomato strain DC3000 in rice, tobacco and Arabidopsis thaliana respectively. While they were normally propagated on the cultural medium supplemented with 2 mM rutin for those pathogenic bacteria. The enhanced resistance was associated with primed expression of several pathogenesis-related genes. We also demonstrated that the rutin-mediated priming resistance was attenuated in npr1, eds1, eds5, pad4-1, ndr1 mutants, and NahG transgenic Arabidopsis plant, while not in either snc1-11, ein2-5 or jar1 mutants. We concluded that the rutin-priming defense signal was modulated by the salicylic acid (SA)-dependent pathway from an early stage upstream of NDR1 and EDS1.201626751786
89110.9404The Arabidopsis flavin-dependent monooxygenase FMO1 is an essential component of biologically induced systemic acquired resistance. Upon localized attack by necrotizing pathogens, plants gradually develop increased resistance against subsequent infections at the whole-plant level, a phenomenon known as systemic acquired resistance (SAR). To identify genes involved in the establishment of SAR, we pursued a strategy that combined gene expression information from microarray data with pathological characterization of selected Arabidopsis (Arabidopsis thaliana) T-DNA insertion lines. A gene that is up-regulated in Arabidopsis leaves inoculated with avirulent or virulent strains of the bacterial pathogen Pseudomonas syringae pv maculicola (Psm) showed homology to flavin-dependent monooxygenases (FMO) and was designated as FMO1. An Arabidopsis knockout line of FMO1 proved to be fully impaired in the establishment of SAR triggered by avirulent (Psm avrRpm1) or virulent (Psm) bacteria. Loss of SAR in the fmo1 mutants was accompanied by the inability to initiate systemic accumulation of salicylic acid (SA) and systemic expression of diverse defense-related genes. In contrast, responses at the site of pathogen attack, including increases in the levels of the defense signals SA and jasmonic acid, camalexin accumulation, and expression of various defense genes, were induced in a similar manner in both fmo1 mutant and wild-type plants. Consistently, the fmo1 mutation did not significantly affect local disease resistance toward virulent or avirulent bacteria in naive plants. Induction of FMO1 expression at the site of pathogen inoculation is independent of SA signaling, but attenuated in the Arabidopsis eds1 and pad4 defense mutants. Importantly, FMO1 expression is also systemically induced upon localized P. syringae infection. This systemic up-regulation is missing in the SAR-defective SA pathway mutants sid2 and npr1, as well as in the defense mutant ndr1, indicating a close correlation between systemic FMO1 expression and SAR establishment. Our findings suggest that the presence of the FMO1 gene product in systemic tissue is critical for the development of SAR, possibly by synthesis of a metabolite required for the transduction or amplification of a signal during the early phases of SAR establishment in systemic leaves.200616778014
46120.9403The pepper Bs4C proteins are localized to the endoplasmic reticulum (ER) membrane and confer disease resistance to bacterial blight in transgenic rice. Transcription activator-like effector (TALE)-dependent dominant disease resistance (R) genes in plants, also referred to as executor R genes, are induced on infection by phytopathogenic bacteria of the genus Xanthomonas harbouring the corresponding TALE genes. Unlike the traditional R proteins, the executor R proteins do not determine the resistance specificity and may function broadly in different plant species. The executor R gene Bs4C-R in the resistant genotype PI 235047 of the pepper species Capsicum pubescens (CpBs4C-R) confers disease resistance to Xanthomonas campestris pv. vesicatoria (Xcv) harbouring the TALE genes avrBsP/avrBs4. In this study, the synthetic genes of CpBs4C-R and two other Bs4C-like genes, the susceptible allele in the genotype PI585270 of C. pubescens (CpBs4C-S) and the CaBs4C-R homologue gene in the cultivar 'CM334' of Capsicum annum (CaBs4C), were characterized in tobacco (Nicotiana benthamiana) and rice (Oryza sativa). The Bs4C genes induced cell death in N. benthamiana. The functional Bs4C-eCFP fusion proteins were localized to the endoplasmic reticulum (ER) membrane in the leaf epidermal cells of N. benthamiana. The Xa10 promoter-Bs4C fusion genes in transgenic rice conferred strain-specific disease resistance to Xanthomonas oryzae pv. oryzae (Xoo), the causal agent of bacterial blight in rice, and were specifically induced by the Xa10-incompatible Xoo strain PXO99(A) (pHM1avrXa10). The results indicate that the Bs4C proteins from pepper species function broadly in rice and the Bs4C protein-mediated cell death from the ER is conserved between dicotyledonous and monocotyledonous plants, which can be utilized to engineer novel and enhanced disease resistance in heterologous plants.201829603592
53130.9399hrp gene-dependent induction of hin1: a plant gene activated rapidly by both harpins and the avrPto gene-mediated signal. Two classes of bacterial genes are involved in the elicitation of the plant hypersensitive response (HR) in resistant plants: hrp genes and avr genes. hrp genes have been shown to be involved in the production and secretion of a new class of bacterial virulence/avirulence proteins, including harpin of Erwinia amylovora and harpinPss of Pseudomonas syringae. The ability of avr genes in the elicitation of the HR/resistance is dependent on functional hrp genes. The relationships between harpins and avr gene products are not known. This study investigates the plant genes induced by harpins and the effect of avr genes on the expression of such plant genes. A tobacco gene highly induced by harpins was isolated by a subtractive hybridization method. Induction of hin1 by P.s. pv. syringae 61 (Pss61) was found to be dependent on functional bacterial hrp genes. P. fluorescens (a saprophyte) or hrp mutants defective in the Hrp secretion pathway did not induce hin1 significantly. A hin 1-related gene in tomato cv. Rio Grande-PtoR was found to be rapidly induced by P. s. pv. tomato T1 (a virulent bacterium on Rio Grande-PtoR) containing the avrPto gene, which mediates the elictation of the HR/resistance in a Pto plant resistance gene-dependent manner. The induction of hin1 by bacteria correlates with production of harpins in planta. The putative open reading frame of hin1 encodes a novel protein of 221 amino acids. The data suggest that harpins and the avrPto-mediated signal induce a common plant gene in the elicitation of the HR.19968893538
37140.9398N-3-Oxo-Octanoyl Homoserine Lactone Primes Plant Resistance Against Necrotrophic Pathogen Pectobacterium carotovorum by Coordinating Jasmonic Acid and Auxin-Signaling Pathways. Many Gram-negative bacteria use small signal molecules, such as N-acyl-homoserine lactones (AHLs), to communicate with each other and coordinate their collective behaviors. Recently, increasing evidence has demonstrated that long-chained quorum-sensing signals play roles in priming defense responses in plants. Our previous work indicated that a short-chained signal, N-3-oxo-octanoyl homoserine lactone (3OC8-HSL), enhanced Arabidopsis resistance to the hemi-biotrophic bacteria Pseudomonas syringae pv. tomato DC3000 through priming the salicylic acid (SA) pathway. Here, we found that 3OC8-HSL could also prime resistance to the necrotrophic bacterium Pectobacterium carotovorum ssp. carotovorum (Pcc) through the jasmonic acid (JA) pathway, and is dependent on auxin responses, in both Chinese cabbage and Arabidopsis. The subsequent Pcc invasion triggered JA accumulation and increased the down-stream genes' expressions of JA synthesis genes (LOX, AOS, and AOC) and JA response genes (PDF1.2 and VSP2). The primed state was not observed in the Arabidopsis coi1-1 and jar1-1 mutants, which indicated that the primed resistance to Pcc was dependent on the JA pathway. The 3OC8-HSL was not transmitted from roots to leaves and it induced indoleacetic acid (IAA) accumulation and the DR5 and SAUR auxin-responsive genes' expressions in seedlings. When Arabidopsis and Chinese cabbage roots were pretreated with exogenous IAA (10 μM), the plants had activated the JA pathway and enhanced resistance to Pcc, which implied that the JA pathway was involved in AHL priming by coordinating with the auxin pathway. Our findings provide a new strategy for the prevention and control of soft rot in Chinese cabbage and provide theoretical support for the use of the quorum-sensing AHL signal molecule as a new elicitor.202235774826
38150.9398Alginate Oligosaccharide (AOS) induced resistance to Pst DC3000 via salicylic acid-mediated signaling pathway in Arabidopsis thaliana. Alginate Oligosaccharide (AOS) is a natural biological carbohydrate extracted from seaweed. In our study, Arabidopsis thaliana was used to evaluate the AOS-induced resistance to Pseudomonas syringae pv. tomato DC3000 (Pst DC3000). Resistance was vitally enhanced at 25 mg/L in wild type (WT), showing the decreased disease index and bacteria colonies, burst of ROS and NO, high transcription expression of resistance genes PR1 and increased content of salicylic acid (SA). In SA deficient mutant (sid2), AOS-induced disease resistance dropped obviously compared to WT. The disease index was significantly higher than WT and the expression of recA and avrPtoB are two and four times lower than WT, implying that AOS induces disease resistance injecting Pst DC3000 after three days treatment by arousing the SA pathway. Our results provide a reference for the profound research and application of AOS in agriculture.201931521273
62160.9397Different 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 oomycete Peronospora parasitica, and to Pseudomonas bacteria expressing the avirulence gene avrRps4. The requirement for NDR1 by these EDS1-dependent R loci is either weak or not measurable. Conversely, three NDR1-dependent R loci, RPS2, RPM1, and RPS5, operate independently of EDS1. Another RPP locus, RPP8, exhibits no strong exclusive requirement for EDS1 or NDR1 in isolate-specific resistance to P. parasitica, although resistance is compromised weakly by eds1. Similarly, resistance conditioned by two EDS1-dependent RPP genes, RPP4 and RPP5, is impaired partially by ndr1, implicating a degree of pathway cross-talk. Our results provide compelling evidence for the preferential utilization of either signaling component by particular R genes and thus define at least two disease resistance pathways. The data also suggest that strong dependence on EDS1 or NDR1 is governed by R protein structural type rather than pathogen class.19989707643
11170.9394Diffusible signal factor primes plant immunity against Xanthomonas campestris pv. campestris (Xcc) via JA signaling in Arabidopsis and Brassica oleracea. BACKGROUND: Many Gram-negative bacteria use quorum sensing (QS) signal molecules to monitor their local population density and to coordinate their collective behaviors. The diffusible signal factor (DSF) family represents an intriguing type of QS signal to mediate intraspecies and interspecies communication. Recently, accumulating evidence demonstrates the role of DSF in mediating inter-kingdom communication between DSF-producing bacteria and plants. However, the regulatory mechanism of DSF during the Xanthomonas-plant interactions remain unclear. METHODS: Plants were pretreated with different concentration of DSF and subsequent inoculated with pathogen Xanthomonas campestris pv. campestris (Xcc). Pathogenicity, phynotypic analysis, transcriptome combined with metabolome analysis, genetic analysis and gene expression analysis were used to evaluate the priming effects of DSF on plant disease resistance. RESULTS: We found that the low concentration of DSF could prime plant immunity against Xcc in both Brassica oleracea and Arabidopsis thaliana. Pretreatment with DSF and subsequent pathogen invasion triggered an augmented burst of ROS by DCFH-DA and DAB staining. CAT application could attenuate the level of ROS induced by DSF. The expression of RBOHD and RBOHF were up-regulated and the activities of antioxidases POD increased after DSF treatment followed by Xcc inoculation. Transcriptome combined with metabolome analysis showed that plant hormone jasmonic acid (JA) signaling involved in DSF-primed resistance to Xcc in Arabidopsis. The expression of JA synthesis genes (AOC2, AOS, LOX2, OPR3 and JAR1), transportor gene (JAT1), regulator genes (JAZ1 and MYC2) and responsive genes (VSP2, PDF1.2 and Thi2.1) were up-regulated significantly by DSF upon Xcc challenge. The primed effects were not observed in JA relevant mutant coi1-1 and jar1-1. CONCLUSION: These results indicated that DSF-primed resistance against Xcc was dependent on the JA pathway. Our findings advanced the understanding of QS signal-mediated communication and provide a new strategy for the control of black rot in Brassica oleracea.202337404719
75180.9392Identification and expression profiling of tomato genes differentially regulated during a resistance response to Xanthomonas campestris pv. vesicatoria. The gram-negative bacterium Xanthomonas campestris pv. vesicatoria is the causal agent of spot disease in tomato and pepper. Plants of the tomato line Hawaii 7981 are resistant to race T3 of X. campestris pv. vesicatoria expressing the type III effector protein AvrXv3 and develop a typical hypersensitive response upon bacterial challenge. A combination of suppression subtractive hybridization and microarray analysis identified a large set of cDNAs that are induced or repressed during the resistance response of Hawaii 7981 plants to X. campestris pv. vesicatoria T3 bacteria. Sequence analysis of the isolated cDNAs revealed that they correspond to 426 nonredundant genes, which were designated as XRE (Xanthomonas-regulated) genes and were classified into more than 20 functional classes. The largest functional groups contain genes involved in defense, stress responses, protein synthesis, signaling, and photosynthesis. Analysis of XRE expression kinetics during the tomato resistance response to X. campestris pv. vesicatoria T3 revealed six clusters of genes with coordinate expression. In addition, by using isogenic X. campestris pv. vesicatoria T2 strains differing only by the avrXv3 avirulence gene, we found that 77% of the identified XRE genes were directly modulated by expression of the AvrXv3 effector protein. Interestingly, 64% of the XRE genes were also induced in tomato during an incompatible interaction with an avirulent strain of Pseudomonas syringae pv. tomato. The identification and expression analysis of X. campestris pv. vesicatoria T3-modulated genes, which may be involved in the control or in the execution of plant defense responses, set the stage for the dissection of signaling and cellular responses activated in tomato plants during the onset of spot disease resistance.200415553246
93190.9391Use of Arabidopsis recombinant inbred lines reveals a monogenic and a novel digenic resistance mechanism to Xanthomonas campestris pv campestris. Infiltration of the Arabidopsis thaliana accession Landsberg erecta (Ler) with Xanthomonas campestris pv campestris isolate 2D520 results in extensive necrosis and limited chlorosis within 5-6 days post-inoculation (d.p.i.), which can lead to systemic necrosis within 23 d.p.i. in contrast, the accession Columbia (Col) remains asymptomatic after infiltration. Although both accessions support bacterial growth, 5-28-fold more bacteria are present in Ler than in Col leaf tissue. Inheritance studies indicate that three independent, dominant or partially dominant, nuclear genes condition resistance to X. c. campestris 2D520. The major gene, termed RXC2, conditions monogenic resistance to X. c.; campestris and was mapped to a 5.5 cM interval of chromosome V. Segregation data indicate that the locus RXC3 in conjunction with RXC4 confers digenic resistance to X. c. campestris. The combined action of RXC3 and RXC4 is correlated with a suppression of in planta bacterial levels and a suppression of symptoms relative to Ler. The RXC3 + RXC4-mediated resistance is novel in that although the Col allele of RXC4 contributes positively to resistance, it is the Ler and not the Col allele of RXC3 that contributes positively to resistance. RXC3 was mapped to the bottom arm of chromosome V in a 2.7 cM interval within the major recognition gene complex MRC-J, a cluster of genes involved in disease resistance. RXC4 was mapped to a 12 cM interval on chromosome II that also contains RXC1, a gene conferring tolerance to X. c. campestris.19979263449