Project description:Some strains of the foliar pathogen Pseudomonas syringae are adapted for growth and survival on leaf surfaces and in the leaf interior. Global transcriptome profiling was used to evaluate if these two habitats offer distinct environments for bacteria and thus present distinct driving forces for adaptation. Further transcriptome profiling was performed to understand the various environmental conditions that P. syringae cells encounter during their association with plants. RNA was collected from P. syringae pv. syringae strain B728a cells that were exposed to seven treatments. The treatments included five in vitro treatments, namely exposing cells to a basal medium, sodium chloride to confer an osmotic stress, hydrogen peroxide to confer an apoplastic growth, iron limitation, nitrogen limitation. They also included two in planta treatments, namely recovering cells from epiphytic sites after surface inoculation and 72 h of growth on bean (Phaseolus vulgaris L.) leaves and recovering cells from apoplastic sites after infiltration and 48 h of growth in bean leaves. The results suggested that B728a cells experience vastly different environments when growing on the surface versus the interior of leaves and identified distinct traits that are likely used for persistence and growth in these environments.
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
Project description:Pseudomonas syringae uses HrpRSL to regulate the expression of type III secretion system (T3SS) genes and bacterial virulence. However, the molecular mechanism and the regulons of HrpRSL have yet to be fully elucidated. Here, we performed chromatin immunoprecipitation followed by high-throughput DNA sequencing (ChIP-seq) on HrpRSL and Lon. The direct regulation of these genes by corresponding regulator has been confirmed by Electrophoretic mobility shift assays (EMSAs) and quantitative real-time polymerase chain reactions (qRT-PCR). Binding motifs are found by using MEME suite and verified by footprint assays in vitro. Collectively, this work provides new cues to better understand the detailed regulatory networks of T3SS systems in P. syringae. ChIP-seq analysis of HrpRSL and Lon in Pseudomonas syringas
Project description:Pseudomonas syringae is an important plant pathogen that infects a wide variety of crops. The mgo (mangotoxin-generating operon) gene cluster produces an extracellular signaling molecule, leudiazen, and is highly conserved in Pseudomonas syringae strains. Here, we genetically removed mgo in Pseudomonas syringae pv. syringae (Pss) UMAF0158 to interrogate its impacts on bacterial infection. Loss of mgo not only alleviated the chlorosis symptom caused by Pss UMAF0158 infection, but also reduced bacterial population in tomato leaflets. Structure-activity relationship revealed that the diazeniumdiolate group and the isobutyl side chain of leudiazen are critical for its signaling activity. Through global transcriptome analysis, we found that mgo regulates the expression of a new gene cluster in addition to mangotoxin biosynthetic operon, namely RS17235-RS17245. This new gene cluster contributes to in planta survival of Pss UMAF0158 and is widely distributed in Pseudomonas syringae strains. Our results demonstrate that chemical signaling systems in plant pathogens play prominent roles in virulence and population increase and set stages for understanding downstream components of mgo-regulated signaling pathways.
Project description:This study evaluates the transcriptome of transgenic Arabidopsis seedlings expressing the effector HopBB1 from the bacteria Pseudomonas syringae