Involvement of GALA effectors in Ralstonia solanacearum disease development towards two host plants

Abstract:

[Objective] By testing the virulence of single and multiple GALA mutants generated in Ralstonia solanacearum strain OE1-1, we evaluated the pathogenicity of these effectors in different host plants.[Methods] The deletion mutant of R. solanacearum OE1-1 was constructed through double crossover. Deletion of the target gene was confirmed by colony PCR. Virulence assay and bacterial multiplication were measured by root-cutting and leaf infiltration respectively. Tobacco (Nicotiana tabacum cv. Bright Yellow) and tomato (Lycopersicon esculentum cv. Moneymaker) were adopted as host plants to inoculate.[Results] Deletion mutants of each effector gene barely affected the bacterial virulence in tobacco. A mutant RK7022 with the deletion of all seven gala genes showed 2-days delayed virulence on tobacco compared with the wild type. The bacterial multiplication capacity of deletion mutants correlated with the phenotypes on host plants. Pathogenicity test on tomato among GALA mutants and wild type OE1-1 showed no difference.[Conclusion] GALA effectors contributed collectively to pathogenicity of OE1-1 on tobacco but not on tomato. Some effectors might play more important roles in R. solanacearum pathogenicity.