Some Type III effectors of Ralstonia solanacearum may suppress host RNA silencing for function

Abstract

Ralstonia solanacearum is a devastating bacterial pathogen responsible for bacterial wilt in various crops. It employs the Type III Secretion System (T3SS) to deliver effectors known as R. solanacearum injected proteins (Rips) into host plant cells. These Rips play a critical role in the pathogenicity of the bacterium, yet their mechanisms of action remain incompletely understood. In this study, we screened 13 Rips from R. solanacearum strain FJ1003 and discovered that RipAW and RipAU possess the ability to suppress RNA silencing, an essential gene regulatory mechanism in plants. Moreover, we demonstrated heightened susceptibility to R. solanacearum and potato virus X in transgenic Nicotiana benthamiana overexpressing RipAW. Silencing of Dicer-like 1 (DCL1) or RNA-dependent RNA polymerase 6 (RDR6) promoted the infection of R. solanacearum in N. benthamiana. Arabidopsis with defects in Argonaute 1 (AGO1), DCL1 or RDR6 also showed increased susceptibility to R. solanacearum compared to wildtype Arabidopsis. These findings collectively suggest a scenario in which certain Rips interfere with host plant RNA silencing, and RNA silencing suppression may be one of the mechanisms employed by Rips to promote virulence.