Results for “RSSC” | PubMed Health

PubMed2026

Characterization and classification of a novel bacteriophage, vB_RsoP_HXg1W, infecting Ralstonia pseudosolanacearum: a new member of the genus Serkorvirus in the family Autotranscriptaviridae.

Bacterial wilt caused by Ralstonia solanacearum species complex (RSSC) is a significant threat to agriculture due to the pathogen's broad host range and persistence in soil. Bacteriophages (phages) are being explored as biocontrol agents, and such strategies are gaining interest. In this study, we isolated and characterized vB_RsoP_HXg1W, a novel phage propagated on R. pseudosolanacearum GMI1000. The phage has a linear double-stranded DNA genome of 40,184 bp with a GC content of 62.3%, and displays an icosahedral head with a short tail. A total of 51 open reading frames (ORFs) were identified, and no tRNA genes were detected. Comparative genomic and phylogenetic analyses revealed that vB_RsoP_HXg1W is closely related to Ralstonia phage p2137, p2106, and RpY2, and clusters within the genus Serkorvirus in the family Autotranscriptaviridae. VIRIDIC analysis revealed a maximum intergenomic similarity of 84.7% to the closest included relative, supporting vB_RsoP_HXg1W as a putative novel species-level member of Serkorvirus. These findings contribute to the understanding of RSSC-infecting phages and provide a foundation for further exploration of phage evolution, host range, and biocontrol relevant traits.

Ralstonia↗

PubMed2025

Sucrose and malic acid in the tobacco plant induce hrp regulon in a phytopathogen Ralstonia pseudosolanacearum.

Genes encoding a type III secretion system in Ralstonia pseudosolanacearum are regulated by HrpB as an hrp regulon and induced only in plants. This study aimed to identify the plant signals that induce the hrp regulon and confirm the signal recognition mechanism. Signaling molecules that induce hrpB expression were screened using resting cells of the hrpB-lacZ reporter strain. Only the soluble fraction of smashed tobacco seedlings induced hrpB expression. The heated soluble fraction retained its hrpB-inducing activity, indicating that the signaling molecules were not proteins. When the soluble fraction was fractionated into acidic, neutral, and basic components, both the acidic and neutral fractions induced hrpB expression. As neutral compounds, sucrose, glucose, and fructose have been found to induce hrpB expression. Sucrose-induced hrpB expression was greatly reduced in the prhA mutant, indicating that the TonB-dependent receptor PrhA perceives sugars. Among the organic acids found in the acidic fractions, malic acid most efficiently induced hrpB expression, which was reduced by the mutation of a hybrid histidine kinase gene of a two-component system, rsc1598, indicating that Rsc1598 may sense malic acid. We demonstrated direct binding of Rsc1598 to malic acid using isothermal titration calorimetry.IMPORTANCESimilar to other Gram-negative plant pathogens, the type III secretion system (T3SS) is the most important virulence factor in Ralstonia pseudosolanacearum. The genes for the T3SS are regulated as an hrp regulon, activated only when the pathogen encounters the plants, indicating that the pathogen must sense plant signals. For the first time, we identified two signaling compounds, sucrose and malic acid, that are abundantly found in tobacco roots. The hrp operon was induced even in non-host plants, possibly because sucrose and malic acid are common in plants. We also found that R. pseudosolanacearum membrane proteins received sucrose and malic acid independently. As a next step, antagonists of signaling molecules can be screened.

Malates↗