243 research outputs found
Transcriptomics-based screen for genes induced by flagellin and repressed by pathogen effectors identifies a cell wall-associated kinase involved in plant immunity
No full textBackground: Microbe-associated molecular patterns, such as those present in bacterial flagellin, are powerful inducers of the innate immune response in plants. Successful pathogens deliver virulence proteins, termed effectors, into the plant cell where they can interfere with the immune response and promote disease. Engineering the plant immune system to enhance disease resistance requires a thorough understanding of its components. Results: We describe a high-throughput screen, using RNA sequencing and virus-induced gene silencing, to identify tomato genes whose expression is enhanced by the flagellin microbe-associated molecular pattern flgII-28, but reduced by activities of the Pseudomonas syringae pv. tomato (Pst) type III effectors AvrPto and AvrPtoB. Gene ontology terms for this category of Flagellin-induced repressed by effectors (FIRE) genes showed enrichment for genes encoding certain subfamilies of protein kinases and transcription factors. At least 25 of the FIRE genes have been implicated previously in plant immunity. Of the 92 protein kinase-encoding FIRE genes, 33 were subjected to virus-induced gene silencing and their involvement in pattern-triggered immunity was tested with a leaf-based assay. Silencing of one FIRE gene, which encodes the cell wall-associated kinase SlWAK1, compromised the plant immune response resulting in increased growth of Pst and enhanced disease symptoms. Conclusions: Our transcriptomic approach identifies FIRE genes that represent a pathogen-defined core set of immune-related genes. The analysis of this set of candidate genes led to the discovery of a cell wall-associated kinase that participates in plant defense. The FIRE genes will be useful for further elucidation of the plant immune system.Fil: Rosli, Hernan Guillermo. Boyce Thompson Institute for Plant Research; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Biotecnológicas. Instituto de Investigaciones Biotecnológicas ; ArgentinaFil: Zhen, Yi. Boyce Thompson Institute for Plant Research; Estados UnidosFil: Pombo, Marina Alejandra. Boyce Thompson Institute for Plant Research; Estados UnidosFil: Zhong, Silin. Boyce Thompson Institute for Plant Research; Estados Unidos. University of Hong Kong; Hong KongFil: Bombarely, Aureliano. Boyce Thompson Institute for Plant Research; Estados UnidosFil: Fei, Zhangjun. Boyce Thompson Institute for Plant Research; Estados UnidosFil: Collmer, Alan. Cornell University; Estados Unidos. King Abdulaziz University; Estados UnidosFil: Martin, Gregory B.. Boyce Thompson Institute for Plant Research; Estados Unidos. Cornell University; Estados Unidos. King Abdulaziz University; Estados Unido
GABA uptake via the GABA permease GabP
No full textThe non-protein amino acid γ-aminobutyric acid (GABA) is the most abundant amino acid in the tomato (Solanum lycopersicum) leaf apoplast and is synthesised by Arabidopsis thaliana in response to infection by the bacterial pathogen Pseudomonas syringae pv. tomato DC3000 (Pst DC3000). High levels of exogenous GABA have previously been shown to repress the expression of the type III secretion system (T3SS) in Pst DC3000, resulting in reduced elicitation of the hypersensitive response (HR) in the non-host plant tobacco (Nicotiana tabacum). This study demonstrates that GABA permease (GabP) provides the primary mechanism for GABA uptake by Pst DC3000, and that the gabP deletion mutant ÎgabP is insensitive to GABA-mediated repression of T3SS expression. ÎgabP displayed an enhanced ability to elicit the HR in young tobacco leaves and in tobacco plants engineered to produce increased levels of GABA, which supports the hypothesis that GABA uptake via GabP acts to regulate T3SS expression in planta. The observation that P. syringae can be rendered insensitive to GABA through loss of gabP, but that gabP is retained by this bacterium, suggests that GabP is important for Pst DC3000 in a natural setting, either for nutrition, or as a mechanism for regulating gene expression
The Erwinia chrysanthemi EC16 hrp/hrc gene cluster encodes an active Hrp type III secretion system that is flanked by virulence genes functionally unrelated to the Hrp system
No full textErwinia chrysanthemi is a host-promiscuous plant pathogen that possesses a type III secretion system (TTSS) similar to that of the host-specific pathogens E. amylovora and Pseudomonas syringae. The regions flanking the TTSS-encoding hrp/hrc gene clusters in the latter pathogens encode various TTSS-secreted proteins. DNA sequencing of the complete E. chrysanthemi hrp/hrc gene cluster and approximately 12 kb of the flanking regions (beyond the previously characterized hecA adhesin gene in the left flank) revealed that the E. chrysanthemi TTSS genes were syntenic and similar (\u3e50% amino-acid identity) with their E. amylovora orthologs. However, the hrp/hrc cluster was interrupted by a cluster of four genes, only one of which, a homolog of lytic transglycosylases, is implicated in TTSS functions. Furthermore, the regions flanking the hrp/hrc cluster lacked genes that were likely to encode TTSS substrates. Instead, some of the genes in these regions predict ABC transporters and methyl-accepting chemotaxis proteins that could have alternative roles in virulence. Mutations affecting all of the genes in the regions flanking or interrupting the hrp/hrc cluster were constructed in E. chrysanthemi CUCPB5047, a mutant whose reduced pectolytic capacity can enhance the phenotype of minor virulence factors. Mutants were screened in witloof chicory leaves and then in potato tubers and Nicotiana clevelandii seedlings. Mu dII1734 insertion in one gene, designated virA, resulted in strongly reduced virulence in all three tests. virA is immediately downstream of hecA, has an unusually low G+C content of 38%, and predicts an unknown protein of 111 amino acids. The E. chrysanthemi TTSS was shown to be active by its ability to translocate AvrPto-Cya (a P. syringae TTSS effector fused to an adenylate cyclase reporter that is active in the presence of eukaryote calmodulin) into N. benthamiana leaf cells. However, VirA(1.61)-Cya was not translocated into plant cells, and virA expression was not affected by mutations in E. chrysanthemi Hrp regulator genes hrpL and hrpS. Thus, the 44-kb region of the E. chrysanthemi EC16 genome that is centered on the hrp/hrc cluster encodes a potpourri of virulence factors, but none of these appear to be a TTSS effector
A Pseudomonas syringae pv. tomato DC3000 mutant lacking the type III effector HopQ1-1 is able to cause disease in the model plant Nicotiana benthamiana.
No full textPseudomonas syringae Pathovars and Related Pathogens- Identification, Epidemiology and Genomics
No full textFreiheit bis zur Ausschweifung. Polen und die Schweiz in der zweiten Hälfte des 18. Jahrhunderts
No full textErwinia chrysanthemi EC16 produces a second set of plant-inducible pectate lyase isozymes
No full textThe enterobacterium Erwinia chrysanthemi causes soft-rot diseases involving extensive tissue maceration in a wide variety of plants and secretes multiple pectic enzymes that degrade plant cell walls and middle lamellae. An E. chrysanthemi mutant with directed deletions or insertions in genes pehX, pelX, pelA, pelB, pelC, and pelE, which encode exo-poly-?-D-galacturonosidase, exopolygalacturonate lyase, and four isozymes of pectate lyase, respectively, was constructed by the marker exchange of a cloned peh
Panicle sterility and grain discolouration : new and emerging bacterial diseases of rice in Italy
No full textIn Italy, panicle sterility and grain discolouration have emerged as serious problems throughout the rice growing areas. Surveys showed that the incidence of panicle sterility was highly variable, varying from low, barely observable in some fields, to more than 50% in other ones. In the Lombardy region the estimated average crop loss due to sterility was 1.1% and 0.1% in 2003 and 2004, respectively. Grain discolouration reduces rice quality. At harvest, susceptible cultivars can have more than 30% discoloured grains. The etiology for both diseases is uncertain and early diagnosis difficult because diseased plants are symptomless. We have demonstrated for the first time that both diseases have a bacterial etiology. Bacterial colonies typical of Acidovorax avenae subsp. avenae were purified from sterile panicles and discoloured rice samples. All recovered strains were confirmed as Aaa by classical PCR using Aaa-specific primers. Isolation of Aaa on a semi-selective agar medium did not always work well. However, an improved BIO-PCR assay was used to test 113 sterile panicle samples and 74% were positive for the presence of Aaa, but negative for Burkholderia glumae (Bg). The bacteria associated with discoloured grains were mostly composed of Pseudomonas and Pantoea species. Based on the 16S rDNA sequences, 85% of the pseudomonads population was classified as P. straminea, P. fulva, P. putida, P. psychrotolerans, P. stutzeri and P. fluorescens. Aaa and Pseudomonas strains were tested for pathogenicity on seedlings in the greenhouse and on plants at the booting stage in the field. Strains of Aaa caused soft rotting of seedlings, panicle sterility and grain discolouration and they showed significant intraspecific variation for virulence. Although most Pseudomonas spp. were not pathogenic, strains of P. stutzeri and strains presumptively identified as P. fulva induced grain discolouration incidence significantly higher than the control. In addition, we have found, for the first time, P. ananatis on rice in Italy
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