Download or read book Identification of Extracellular Components and Early Regulation Steps in the Type III Secretion System of Pseudomonas Syringae written by Joanne Elena Morello and published by . This book was released on 2008 with total page 244 pages. Available in PDF, EPUB and Kindle. Book excerpt: The type III secretion system (T3SS) is a common and important mechanism of pathogenesis for many bacterial pathogens of plants and animals. T3SSs deliver bacterial proteins, called effectors, into the host cell where they suppress host defenses and allow bacterial proliferation and disease. The plant pathogen Pseudomonas syringae has a T3SS that is required for its ability to cause disease on many species of plants. Understanding the T3SS is therefore essential in our effort to understand pathogenesis. We are interested in how the T3SS has evolved for plant pathogenesis. Overall this work seeks to identify components of the T3SS that aid in delivery of effectors across plant barriers, and also to develop tools for studying the T3SS in planta. The T3SS is encoded by a cluster of genes called hrp/hrc genes. In this study we first phenotypically characterized hrp genes of unknown or only postulated function. Hrp proteins were screened for their ability to be substrates of the T3SS, and hrp mutants were tested for their ability to cause a hypersensitive response on non-host plants, translocate an effector into plants, and secrete an effector in vitro. One of these proteins, HrpP, was chosen for additional characterization. We show that HrpP is translocated into plant cells at levels equivalent to effectors and is essential for the function of the T3SS. We found that HrpP from different P. syringae pathovars can complement a hrpP mutant. We also analyzed the complementation ability of truncations of HrpP and an impassible HrpP-GFP fusion to determine the role of HrpP translocation for its function. HrpP was also found to be essential for secretion of all T3SS substrates examined, though a hrpP mutant does secrete reduced levels of the pilus subunit HrpA. Finally, a lux reporter assay was developed to assess hrp promoter activity in planta. We used this assay to test expression in response to PAMP-triggered immunity, in different hrp mutant backgrounds, and to compare in vitro and in planta responses. Due to this work we have a better understanding of P. syringae's T3SS and how it might operate in planta.

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 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 Pseudomonas Syringae Pathogenesis written by and published by . This book was released on 2004 with total page 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 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:

Download or read book The Hypersensitive Reaction in Plants to Pathogens written by Robert N. Goodman and published by American Phytopathological Society. This book was released on 1994 with total page 266 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nikolai Gogol’s short story is a sublime work of tragi-comedy. In it, he brilliantly ridicules the Ukrainian passion for litigation and reveals life as something really rather absurd. Ivan Ivanovich and Ivan Nikiforovich are the greatest of friends—until the day they begin a foolish quarrel that culminates in that very worst of insults: “And you, Ivan Ivanovich, are a goose.” From that moment on, not another word is spoken between them as they choose instead to fight out their differences in the courts. But it seems theirs is a lawsuit that is set to run for years and years.

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 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 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 Identification and Characterization of Pseudomonas Syringae Type Three Effectors that Alter Auxin Responses written by Maria Soledad Nievas and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book An In depth Analysis of Iron and Pathogenicity Regulatory Pathways in Pseudomonas Syringae Pv Syringae B728a written by Jessica Williams Greenwald and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Pseudomonas syringae pv. syringae strain B728a (P.s.s. B728a) is an economically significant plant pathogen that is capable of successful epiphytic colonization of leaf surfaces. Although the virulence factors associated with this pathogen's ability to cause disease have been well studied, the transition from epiphyte to pathogen is not well understood. The research described in this dissertation utilizes high throughput sequencing transcriptome analyses to define an iron regulatory network that is predicted to be utilized during the epiphytic portion of the P.s.s. B728a lifecycle. This dissertation also describes a collaborative microarray analysis that analyzes the P.s.s. B728a transcriptome at a global level. An iron associated sigma factor, AcsS, encoded within a peptide synthesis rich region of the P.s.s. B728a genome is shown to regulate the citrate siderophore achromobactin. RNA-seq transcriptome analysis reveals that this sigma factor regulates expression of genes predicted to be involved in functions that are important during the epiphytic stage of P.s.s. B728a, including genes involved in iron response, secretion, extracellular polysaccharide production, and cell motility. As part of a collaboration, the transcriptomes of the P.s.s. B728a genome and nine deletion mutants in regulatory genes were analyzed by microarray analayses using seven treatment conditions, including epiphytic and in planta conditions. As part of these microarray analyses, results are described for the global regulator, GacS, and a downstream transcription factor, SalA. This study confirms the role of GacS and SalA in the regulation of major virulence components of P.s.s. B728a such as phytotoxin production and Type III secretion. This study also elucidates a role for GacS and SalA regulation of genes important for epiphytic survival and function, including the Type VI secretion system, iron acquisition, and EPS production.

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 The Pseudomonas Syringae Type III Secretion System written by Emerson Crabill and published by . This book was released on 2012 with total page 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 Phytopathogenic Prokaryotes written by Mark S. Mount and published by . This book was released on 1982 with total page 568 pages. Available in PDF, EPUB and Kindle. Book excerpt: V.1 - Phytopathogenic prokaryotes; Concepts for plant interactions with prokaryotes; Prokaryote interactions on plant surfaces; Prokaryote interactions within the plant; v.2 - Epidemiology and dispersal; Host coevolution with the pathogen; Pathogen coevolution with the host; Strategies for control; Cultivation and preservation.

Download or read book Regulation of Bacterial Virulence written by Michael L. Vasil and published by American Society for Microbiology Press. This book was released on 2012-12-05 with total page 1189 pages. Available in PDF, EPUB and Kindle. Book excerpt: A comprehensive compendium of scholarly contributions relating to bacterial virulence gene regulation. • Provides insights into global control and the switch between distinct infectious states (e.g., acute vs. chronic). • Considers key issues about the mechanisms of gene regulation relating to: surface factors, exported toxins and export mechanisms. • Reflects on how the regulation of intracellular lifestyles and the response to stress can ultimately have an impact on the outcome of an infection. • Highlights and examines some emerging regulatory mechanisms of special significance. • Serves as an ideal compendium of valuable topics for students, researchers and faculty with interests in how the mechanisms of gene regulation ultimately affect the outcome of an array of bacterial infectious diseases.