Project description:We implemented transcriptional analysis methods using cDNA and high-throughput sequencing data to identify HrpL-regulated genes for six strains of Pseudomonas syringae
Project description:Pseudomonas syringae, a Gram-negative plant pathogen, infects more than 50 crops with its type III secretion system (T3SS) and causes severe economic losses around the world. Although the mechanisms of virulence-associated regulators of P. syringae T3SS have been studied for decades, the crosstalk and network underlying these regulators are still elusive. Previously, we have individually studied a group of T3SS regulators, including AefR, HrpS, and RhpRS. In the present study, we found 4 new T3SS regulator genes (envZ, ompR, tsiS and phoQ) via transposon-mediated mutagenesis. Two-component systems EnvZ and TsiS natively regulate T3SS. In order to uncover the crosstalk between 16 virulence-associated regulators, (including AefR, AlgU, CvsR, GacA, HrpL, HrpR, HrpS, MgrA, OmpR, PhoP, PilR, PsrA, RhpR, RpoN, TsiR and Vfr) in P. syringae, we mapped an intricate network named PSVnet (Pseudomonas syringae Virulence Regulatory Network) by combining differentially expression genes in RNA-seq and binding loci in ChIP-seq of all regulators.
Project description:We implemented transcriptional analysis methods using cDNA and high-throughput sequencing data to identify HrpL-regulated genes for six strains of Pseudomonas syringae Each Pseudomonas syringae strains was transformed with either pBAD::EV or pBAD containing native hrpL sequence. Strains were grown in MM media supplemented with arabinose and collected 1, 3, and 5 hours post arabinose treatment. RNA was extracted for each time point and mixed at a 1/3 ratio. After removal of rRNA, double stranded cDNA was generated and library prepared accordeing to Illumina protocols.
Project description:Although the ubiquitous bacterial secondary messenger cyclic diguanylate (c-di-GMP) plays important roles in various cellular functions including the formation of biofilm in a wide range of bacteria, its function in model plant pathogen Pseudomonas syringae is largely elusive. In order to test this in P. syringae, we overexpressed a diguanylate cyclase (YedQ) and a phosphodiesterase (YhjH) that are originally from Escherichia coli, resulting in high and low c-di-GMP levels in P. syringae, respectively. Through performing genome-wide RNA sequencing of these two strains, we found that c-di-GMP regulates (i) fliN, fliE and flhA genes, which are associated with flagellar assembly, (ii) alg8 and alg44, which are related to exopolysaccaride biosynthesis pathway, (iii) pvdE, pvdP and pvsA genes, related to siderophore biosynthesis pathway, and (iv) sodA, which is a superoxide dismutase. In particular, we identified five genes sensitive to elevated c-di-GMP level and constructed five luciferase-based reporters that effectively respond to intracellular level of c-di-GMP in P. syringae, which can be used to measure c-di-GMP levels in vivo in the future. Based on the RNA-seq results, phenotypic assays confirmed that c-di-GMP regulated many important biological pathways in P. syringae, such as negative regulation of type III secretion system (T3SS) and motility as well as positive regulation of EPS production, siderophore production and oxidative stress resistance. Taken together, the present study demonstrated that c-di-GMP is closely related to virulence and stress response in P. syringae, suggesting that tuning its level can be a new strategy to protect plants from the attack of this pathogen in the future.
Project description:Pseudomonas syringae was grown on minimal media and King's B medium. The goal of this project was to generate pilot data in preparation for a summer course on high-throughput sequencing where participants prepared their own RNA-Seq libraries and analyzed the resulting data. The summer course was funded by NIH grant 5R25EB023928-03 "A hands-on, integrative next-generation sequencing course: design, experiment, and analysis".