Download or read book Environmental and Density dependent Modulation of Type III Secretion System Genes in Pseudomonas Syringae Pv Tomato DC30 written by and published by . This book was released on 2010 with total page 121 pages. Available in PDF, EPUB and Kindle. Book excerpt: Pseudomonas syringae pathovar tomato strain DC3000 is a model bacterial plant-pathogen that utilizes a dedicated protein export apparatus, the type III secretion system (T3SS), to translocate virulence proteins called effectors directly into host cells. Because effectors suppress plant immune responses, activation of the T3SS is critical upon entry into the host. The P. syringae T3SS is controlled by the hrpRS-hrpL regulatory cascade, and is activated quickly by specific conditions. Different environmental stimuli have been reported to modulate T3SS gene expression in culture, however it is unclear how each signal affects hrpRS or hrpL. My objective was to identify how environmental variables activate or repress hrpRS or hrpL in Pst DC3000. To this aim, I created three T3SS::gusA transcriptional reporter strains by fusing a promoterless gusA after hrpRS, hrpL, and a downstream effector gene, avrPto in the chromosome of Pst DC3000. I then analyzed GUS activity of each reporter strain cultured under variable conditions. I verified that repression of Pst DC3000 T3SS genes in KB acts upstream of the hrpRS operon, and that this repression is relieved by overexpression of either hrpR or hrpS. Furthermore, I demonstrated that hrpRS, hrpL, and avrPto, are differentially regulated by pH and carbon sources, although all carbon source tested (including sugars, a sugar alcohol, glycerol, and organic acids) initially induced T3SS gene expression. Results of several assays suggest that quorum sensing may be involved in regulation of the T3SS in Pst DC3000. First, T3SS genes were optimally expressed when growth media contained carbon sources that promoted slower growth, and when bacteria were cultured at low cell densities. In addition, I show that a T3SS repressive signal accumulated in high cell density Pst DC3000 cultures. However, density-dependent repression of T3SS genes was independent of psyRI, which mediates quorum sensing by acyl homoserine lactones (AHLs), and T3SS gene expression was unaffected by addition of 3-oxo-C6 or C6 AHLs. In contrast, T3SS genes were repressed when another small molecule produced by P. syringae, the auxin IAA, is added to Pst DC3000 cultures. However the biological relevance of IAA as a T3SS repressing signal remains to be explored.
Download or read book Environmental and Density dependent Modulation of Type III Secretion System Genes in Pseudomonas Syringae Pv Tomato DC3000 written by Jennifer L. Stauber and published by . This book was released on 2010 with total page 242 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Regulation of Virulence in the Plant Pathogen Pseudomonas Syringae Pv Tomato DC3000 written by Hanh Ngoc Lam and published by . This book was released on 2014 with total page 474 pages. Available in PDF, EPUB and Kindle. Book excerpt: The type III secretion system (T3SS) is required for virulence of the gram-negative plant pathogen Pseudomonas syringae pv. tomato DC3000 (DC3000) in tomato and Arabidopsis. The alternative sigma factor HrpL directly regulates expression of T3SS genes by binding to a short DNA sequence designated as the "hrp promoter". The ability of DC3000 to colonize plants, subdue multiple layers of plant defense and multiply in plant tissues relies on the activities carried out by the many T3SS regulon members (known collectively as hrp genes). Efforts to identify genes involved in pathogenicity were initiated over three decades ago. However, HrpL binding to hrp promoters has never been directly demonstrated and it is unclear if the list of HrpL-regulated genes is complete. The first goal of the research described here was to systemically and exhaustively identify HrpL-binding sites and likely hrp promoters in the DC3000 genome. Employing chromatin immuno-precipitation, coupled with high-throughput sequencing (ChIP-Seq) and transcription start site analysis (modified RNA-Seq), we found twenty sites representing novel hrp promoters. Using deletion analysis, we attempted to determine if the genes downstream from a subset of these promoters could be linked to virulence. However, the deletions did not affect the hypersensitive response or in planta growth of the resulting strains. Interestingly, many new HrpL regulon members appear to be unrelated to the T3SS (based on their annotations), and orthologs for some of these can be identified in non-pathogenic bacteria. The connection of these new HrpL regulon members to virulence is not obvious. The HrpL regulon is activated as a result of a chain of events, most of which are not well understood. It is known that RpoN, which controls the transcription of hrpL in DC3000, is required for virulence in several bacterial species. Motivated by the hypothesis that genes are coordinately regulated in order to serve a strategic purpose (e.g., virulence), our second goal was to look for other genes activated by RpoN in parallel with hrpL. RpoN ([sigma]54) requires specialized enhancer-binding proteins (EBPs) in order to activate transcription. This arrangement presumably allows the cell to respond to environmental signals by modifying the transcription of particular genes. Using ChIP-Seq and RNA-Seq, we identified candidate RpoN-dependent genes as well as genes that were differentially expressed under hrp-inducing conditions. This initial survey includes more than 200 likely RpoN-regulated genes involved in flagella biosynthesis, energy metabolism, nitrogen metabolism, transport and binding proteins, and small noncoding RNAs, as well as putative regulatory proteins and EBPs. Among the genes that were differentially regulated between hrp-inducing and repressing conditions, more than one dozen appear to be regulated by RpoN and are therefore potentially important in functions related to plant association or virulence.
Download or read book Pseudomonas syringae and related pathogens written by Nicola Sante Iacobellis and published by Springer Science & Business Media. This book was released on 2013-06-29 with total page 673 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume mainly reports on new and recent advancements on different aspects of Pseudomonas syringae, a plant pathogenic bacterial species that include a high number of pathogens of important crops, which is an interesting model organism in plant pathology. In addition some related fluorescent Pseudomonas spp., responsible of new and emerging diseases, as well as some pathogens previously included in the above genus and now classified in the genera Ralstonia, Acidovorax are also considered. The tremendous recent advancements on: the ecology and epidemiology and, in particular, the adaptation of P. syringae to stresses and adverse environmental conditions; the function and regulation of genes involved in the production of phytotoxins and on their mechanism of action in the interaction with the host cells; the structure, function and regulation of type three secretion system (TTSS) and the transport of the effectors proteins in the host cells; the possibility to control diseases through the induction of the systemic acquired resistance (SAR); the development of molecular techniques for the highly specific and sensible identification and detection of pathogens; the determination of the causal agents of new and emerging diseases as well the classification of the different pathovars of P. syringae; are reported in 76 chapters cured by leading scientist in the respective fields.
Download or read book Regulation of Type III Secretion System in Pseudomonas Syringae written by and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: P. syringae is a group of bacterial phytopathogens that can infect a wide variety of plants. These bacteria rely on the type III secretion system (TTSS) to deliver effectors into plant cells for infection. The TTSS genes, that encode the TTSS apparatus and the effectors, are repressed when bacteria grow in nutrient rich media but are strongly induced in the plants and in minimal medium (MM). Plant cutin monomers appear to negatively regulate the P. syringae TTSS genes. It is poorly understood how bacteria sense the environmental signals to regulate the TTSS genes. By genetic screen, four sets of transposon insertion mutants displaying aberrant TTSS gene expression were isolated: KB and fin mutants derepress the TTSS genes in rich medium KB and in the presence of a cutin monomer precursor in MM, respectively; min and pin mutants are defective in induction of TTSS genes in MM and in plants, respectively. A putative two-component sensor histidine kinase, RohS, is identified to be required for the induction of avrPto-LUC in MM and in plants. The rohS gene is in an operon containing a two-component response regulator gene rohR. Mutation of rohS in P. s. phaseolicola and P. s. tomato reduced the bacterial pathogenicity on hosts and HR-inducing activity on non-hosts. Our results suggested that RohS acts upstream of HrpR/HrpS. The phosphorylated RohR represses TTSS genes. It is likely that RohS acts as phosphatase of RohR in the TTSS-inducing conditions, and subsequently derepresses TTSS genes. Simple sugars such as glucose, sucrose and fructose are known to be inducers of the TTSS genes. Isolation of four min mutants defective in fructose-uptake enabled us to study if sugars serve as extracellular signals or as essential nutrients. Our results suggest that fructose acts as an essential nutrient for the activation of type III genes. These mutants slightly compromised induction of avrPto promoter in Arabidopsis and pathogenicity on the host bean plant, but displayed normal HR elicitation on non-host plant tobacco. The reduced pathogenicity suggested that exploitation of fructose from the host tissue is an important means for pathogenesis of P. s. phaseolicola.
Download or read book Characterization of the Regulatory Network of the Type III Secretion System in Pseudomonas Syringae Pv Tomato DC3000 microform written by Amanda Zhenhua Liu and published by National Library of Canada = Bibliothèque nationale du Canada. This book was released on 2002 with total page 196 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Characterization of Effectors from the Type III Protein Secretion System of Pseudomonas Syringae Pv Tomato DC3000 written by Misty D. Janes Wehling and published by . This book was released on 2004 with total page 328 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Patrum aegyptorum opera omnia written by and published by . This book was released on 1858 with total page 15 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Analysis of the Flagellar and HRP Type III Secretion System in the Plant Bacterial Pathogen Pseudomonas Syringae Pv Tomato DC3000 written by Jennifer M. Hesson and published by . This book was released on 2008 with total page 348 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Regulation of the Hrp Type III Secretion System in Pseudomonas Syringae Pv Tomato DC3000 written by and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Pseudomonas Syringae Type III Secretion System and Effectors written by Zhengqing Fu and published by ProQuest. This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Type III Secretion System of Phytopathogenic Bacterium Pseudomonas Syringae written by Chun-Mei Li and published by . This book was released on 2007 with total page 64 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Type III Virulence Effectors of Pseudomonas Syringae Pv Tomato Strain DC3000 written by Sruti Bandyopadhyay and published by . This book was released on 2003 with total page 396 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Pseudomonas Syringae Type III Secretion System written by Fang Tian and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Identification and Secretion of Effectors from the Pseudomonas Syringae Type III Secretion System written by and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
