Project description:We found the Type III effector protein RipAB could suppress multiple plant immune responses and is important for the virulence of bacterial wilt pathogen Ralstonia solanacearum.
Project description:Chickpea (Cicer arietinum) is the third largest legume grown worldwide and are prone to drought and various pathogen infections. These stresses often occur concurrently in the field conditions. Previous studies in other plant species indicated that plant senses concurrently occurring stresses as new state of stress however, the molecular events in response to that is largely unknown. In the present study, we studied the transcriptome changes in chickpea plants exposed to combination of drought stress and a potential wilt pathogen, Ralstonia solanacearum by microarray analysis. Chickpea plants were exposed to short duration individual drought (SD-drought, soil field capacity, FC-35%), long duration individual drought (LD-drought, FC-30%), short duration individual pathogen stress (SD-pathogen = 2 days pathogen infection), long duration individual pathogen stress (LD-pathogen = 4 days of infection) and short duration and long duration combined stress, SD-combined = 2 days of pathogen infection with progressive drought (FC-40% to FC- 35%), LD combined = 4 days of pathogen infection with progressive drought (FC-35% to 30%).Transcriptome analysis for the leaf samples from above treatment were done by microarray analysis using Agilent ChickpeaGXP_8X60K chip. Result indicated presence of specific molecular events and also some common but tailored events in response to combined stress. Global transcriptional analysis in chickpea leaves exposed to individual and combined drought stress and Ralstonia solanacearum infection.
Project description:The Ralstonia solanacearum species complex includes R. solanacearum, R. syzygii, and the Blood Disease Bacterium (BDB). All colonize plant xylem vessels and cause wilt diseases, but with significant biological differences. R. solanacearum is a soilborne bacterium that infects the roots of a broad range of plants. R. syzygii causes Sumatra disease of clove trees and is actively transmitted by cercopoid insects. BDB is also pathogenic to a single host, banana, and is transmitted by pollinating insects. Sequencing and DNA-DNA hybridization studies indicated that despite their phenotypic differences, these three plant pathogens are actually very closely related, falling into the Phylotype IV subgroup of the R. solanacearum species complex. To better understand the relationships among these bacteria, we sequenced and annotated the genomes of R. syzygii strain R24 and BDB strain R229. These genomes were compared to strain PSI07, a closely related Phylotype IV tomato isolate of R. solanacearum, and to five additional R. solanacearum genomes. Whole-genome comparisons confirmed previous phylogenetic results: the three phylotype IV strains share more and larger syntenic regions with each other than with other R. solanacearum strains. Furthermore, the genetic distances between strains, assessed by an in-silico equivalent of DNA-DNA hybridization, unambiguously showed that phylotype IV strains of BDB, R. syzygii and R. solanacearum form one genomic species. Based on these comprehensive data we propose a revision of the taxonomy of the R. solanacearum species complex. The BDB and R. syzygii genomes encoded no obvious unique metabolic capacities and contained no evidence of horizontal gene transfer from bacteria occupying similar niches. Genes specific to R. syzygii and BDB were almost all of unknown function or extrachromosomal origin. Thus, the pathogenic life-styles of these organisms are more probably due to ecological adaptation and genomic convergence during vertical evolution than to the acquisition of DNA by horizontal transfer.
Project description:Ralstonia syzygii subsp. indonesiensis (Rsi, former name: Ralstonia solanacearum phylotype IV) PW1001, a causal agent of potato wilt disease, induces hypersensitive response (HR) on its non-host eggplant (Solanum melongena cv. Senryo-nigou). The disaccharide trehalose is involved in abiotic and biotic stress tolerance in many organisms. We found that trehalose is required for eliciting HR on eggplant by plant pathogen Rsi PW1001. In R. solanacearum, it is known that the OtsA/OtsB pathway is the dominant trehalose synthesis pathway, and otsA and otsB encode trehalose-6-phosphate (T6P) synthase and T6P phosphatase, respectively. We generated otsA and otsB mutant strains and found that these mutant strains reduced the bacterial trehalose concentration and HR induction on eggplant leaves compared to wild-type. Trehalose functions intracellularly in Rsi PW1001 because addition of exogenous trehalose did not affect the HR level and ion leakage. Requirement of trehalose in HR induction is not common in R. solanacearum species complex because mutation of otsA in Ralstonia pseudosolanacearum (former name: Ralstonia solanacearum phylotype I) RS1002 did not affect HR on the leaves of its non-host tobacco and wild eggplant Solanum torvum. Further, we also found that each otsA and otsB mutant had reduced ability to grow in a medium containing NaCl and sucrose, indicating that trehalose also has an important role in osmotic stress tolerance.