Characterization of Two Sigma Factors in Plant Pathogenesis by Pseudomonas Syringae Pv. Syringae B728a PDF Download
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Author: Poulami Basu Thakur
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Languages : en
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Author: Poulami Basu Thakur
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Category :
Languages : en
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Author: Amber Lorge
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Languages : en
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Gene regulation in bacteria is highly complex and requires the activity of sigma factors that function as transcriptional regulators. In Pseudomonas syringae pv. syringae B728a, 14 sigma factors have been identified. One of the more interesting is rpoN, encoding Sigma 54, which was initially described for its role in nitrogen utilization and later shown to be involved in regulating adhesion, motility, toxin production, and pathogenicity. The only commonality identified amongst these genes is that gene regulation by Sigma 54 is not essential for normal growth and development because mutational inactivation of rpoN is not lethal. Unlike Sigma 70, which recognizes promoter sites located at positions -10/-35 upstream of the transcription initiation site, Sigma 54 recognizes sites located at positions -12/-24. P.s. pv. syringae B728a encodes an RpoN that shares 80-98% identity with other Pseudomonas species. Promoter scans were conducted on the B728a genome to look for probable binding sites of RpoN. Analysis revealed that RpoN may be involved in regulating genes encoding ABC transporters, drug efflux pumps, flagella proteins, nitrate transporters, and several regulatory proteins. An insertional mutation in the rpoN gene was constructed in the B728a genome and a phenotypic analysis was initiated. Decreased swarming and adhesion ability of the rpoN mutant was observed as compared to B728a. The ability to utilize sole nitrogen sources was also affected. The rpoN mutant showed little or no growth on sole nitrogen sources such as alanine, histidine, lysine, and serine. Pathogenicity was shown to require a functional RpoN, as both HR and disease development was effected by an rpoN mutation. Pseudomonas syringae pv. syringae is most known for the production of two phytotoxins. Unlike RpoN in other species, in P.s. pv. syringae B728a it appears to indirectly down regulate toxin production of syringomycin and syringopeptin. The goal of this study was to characterize some of the important roles RpoN is known to possess and to understand its role in the plant pathogenic and epiphytic lifestyle of P. s. pv. syringae B728a.
Author: Vanessa Lynn Vaughn
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Languages : en
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Pseudomonas syringae pv. syringae B728a, causal agent of brown spot on bean, is an economically important plant pathogen that utilizes extracellular signaling to initiate a lifestyle change from an epiphyte to a pathogen. LuxR regulatory proteins play an important role in the transcriptional regulation of a variety of biological processes involving two-component signaling, quorum sensing, and secondary metabolism. Analysis of the B728a genome identified 24 LuxR-like proteins, three of which are salA, syrF, and syrG located adjacent to the syringomycin gene cluster. All three proteins exhibit domain architecture that placed these LuxR-like proteins into a subfamily of LuxR's associated with regulation of secondary metabolism in Pss B728a. The transcriptional start sites of salA, syrG, and syrF were located 63, 235, and 498 bp upstream of the start codons, respectively, using primer extension analysis. The predicted -10/-35 promoter region of syrF and syrG was confirmed using site-directed mutagenesis and GFP reporters that showed there were conserved promoter sequences observed around the -35 promoter region. It has been established that SalA binds to the promoter of syrF, therefore these conserved promoter sequences serve as the putative binding site for SalA. Deletion mutants of salA, syrF, and syrG failed to produce syringomycin and displayed reduction of virulence on bean. QRT-PCR analysis results revealed that both syrG and syrF are highly expressed in the apoplast indicating that they encode important transcriptional regulators of genes critical to the plant-pathogen interaction. Additionally, this report showed that syrG and syrF are important transcriptional regulators of syringomycin biosynthesis genes, but are not involved in the regulation of virulence genes that reside outside of the syr-syp gene cluster. Overexpression analysis and GFP reporters identified SyrG as an upstream transcriptional activator of syrF, where both SyrG and SyrF activate promoters of syringomycin biosynthesis genes. This study demonstrates that the interaction between SalA, SyrG, and SyrF for the regulation of syringomycin is complex requiring further investigation. The electronic version of this dissertation is accessible from http://hdl.handle.net/1969.1/152526
Author: Angela Renee Records
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Languages : en
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Pseudomonas syringae is a pathogen of numerous plant species, including several economically important crops. P. syringae pv. syringae B728a is a resident on leaves of common bean, where it utilizes several well-studied virulence factors, including secreted effectors and toxins, to develop a pathogenic interaction with its host. The B728a genome was recently sequenced, revealing the presence of 1,297 genes with unknown function. This dissertation demonstrates that a 29.9-kb cluster of genes in the B728a genome encodes a novel secretion pathway, the type VI secretion system (T6SS), that functions to deliver at least one protein outside of the bacterial cell. Western blot analyses show that this secretion is dependent on clpV, a gene that likely encodes an AAA+ ATPase, and is repressed by retS, which apparently encodes a hybrid sensor kinase. RetS and a similar protein called LadS are shown to collectively modulate several virulence-related activities in addition to the T6SS. Plate assays demonstrate that RetS negatively controls mucoidy, while LadS negatively regulates swarming motility. A mutation in retS affects B728a population levels on the surface of bean leaves. A model for the LadS and RetS control of B728a virulence activities is proposed, and possible roles for the B728a T6SS are addressed.
Author: Jessica Williams Greenwald
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Languages : en
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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.
Author: Tahina Onina Ranaivoarisoa
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Category : Electronic dissertations
Languages : en
Pages : 68
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Pseudomonas syringae is a bacterial plant pathogen that infects a large variety of agricultural crops. Bacteria colonize leaf surfaces and enter plant mesophyll tissue through wounds or stomata. Once inside, P. syringae can alter plant cell signaling pathways and suppress plant defense responses enabling it to grow in the intercellular space in the mesophyll. P. syringae possesses at least two types of virulence factors that suppress plant defense responses: i) small phytotoxin molecules, and ii) effector proteins that are translocated through specialized secretion systems. Gram-negative bacteria possess at least six types of secretion systems. The P. syringae type II and type III secretion systems (T2SS and T3SS) are both involved in secreting proteins that are important for P. syringae pathogenesis. Functions of the other secretion systems have not been explored. This study investigates the role of the newly discovered type VI secretion system (T6SS) in P. syringae interaction with plants. The results show that T6SS genes are expressed in three sequenced strains of P. syringae, P. syringae pv. tomato DC3000 (Pst DC3000), P. syringae pv. phaseolicola 1448a (Psp 1448a) and P. syringae pv. syringae B728a (Pss B728a). The T6SSs of Psp 1448a and Pss B728a were also able to secrete the Hcp protein into culture supernatants, showing that they are active. In planta virulence and growth studies revealed that the T6SS may not be essential for Psp 1448a and Pss B728a to cause disease in host plants. However, the T6SS may be involved in regulating biofilm formation, since a mutant Psp 1448a T6SS formed denser biofilm than the wild-type bacteria. These results suggest that the T6SS may secrete factors important for controlling bacterial aggregation on leaves.
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Category :
Languages : en
Pages : 15
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Publisher: ScholarlyEditions
ISBN: 1481661574
Category : Medical
Languages : en
Pages : 164
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Pseudomonas: New Insights for the Healthcare Professional: 2013 Edition is a ScholarlyBrief™ that delivers timely, authoritative, comprehensive, and specialized information about Additional Research in a concise format. The editors have built Pseudomonas: New Insights for the Healthcare Professional: 2013 Edition on the vast information databases of ScholarlyNews.™ You can expect the information about Additional Research in this book to be deeper than what you can access anywhere else, as well as consistently reliable, authoritative, informed, and relevant. The content of Pseudomonas: New Insights for the Healthcare Professional: 2013 Edition has been produced by the world’s leading scientists, engineers, analysts, research institutions, and companies. All of the content is from peer-reviewed sources, and all of it is written, assembled, and edited by the editors at ScholarlyEditions™ and available exclusively from us. You now have a source you can cite with authority, confidence, and credibility. More information is available at http://www.ScholarlyEditions.com/.
Author: Francis Martin
Publisher: John Wiley & Sons
ISBN: 0470958227
Category : Science
Languages : en
Pages : 442
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Plants and microbes interact in a complex relationship that can have both harmful and beneficial impacts on both plant and microbial communities. Effectors, secreted microbial molecules that alter plant processes and facilitate colonization, are central to understanding the complicated interplay between plants and microbes. Effectors in Plant-Microbe Interactions unlocks the molecular basis of this important class of microbial molecules and describes their diverse and complex interactions with host plants. Effectors in Plant Microbe Interactions is divided into five sections that take stock of the current knowledge on effectors of plant-associated organisms. Coverage ranges from the impact of bacterial, fungal and oomycete effectors on plant immunity and high-throughput genomic analysis of effectors to the function and trafficking of these microbial molecules. The final section looks at effectors secreted by other eukaryotic microbes that are the focus of current and future research efforts. Written by leading international experts in plant-microbe interactions, Effectors in Plant Microbe Interactions, will be an essential volume for plant biologists, microbiologists, pathologists, and geneticists.
Author: P.A.H.M. Bakker
Publisher: Springer Science & Business Media
ISBN: 1402067763
Category : Science
Languages : en
Pages : 127
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In the context of increasing concern for food and environmental quality, use of Plant Growth-Promoting Rhizobacteria (PGPR) for reducing chemical inputs in agriculture is a potentially important issue. This book provides an update by renowned international experts on the most recent advances in the ecology of these important bacteria, the application of innovative methodologies for their study, their interaction with the host plant, and their potential application in agriculture.
