Suppression of host plant defense by bacterial small RNAs packaged in outer membrane vesicles

The delivery of noncoding small RNAs (sRNAs) packaged in bacterial outer membrane vesicles (OMVs) can function as novel mediators of interspecies communication. Although the role of bacteria sRNAs in enhancing virulence is well established, the potential role of molecules in the interaction between phytopathogenic bacteria OMVs and their host plants remains unclear. In this study, we employed RNA-Seq to characterize the differentially packaged sRNAs in the pathogen Xanthomonas oryzae pv. oryzicola (Xoc) OMVs. Our candidate sRNA (Xosr001), was found to be abundant in OMVs, and we observed its involvement of sRNA Xosr001 in regulation of OsJMT1, which employ the stomatal immune of host plant for virulence. Xoc loads Xosr001 into OMVs, which are specifically transferred into the mechanical tissues of rice leaves. Xosr001 act as an inhibitors to attenuate OsJMT1 transcripts in vivo and reduce the endogenous MeJA contents in rice leaves. Furthermore, Xosr001 was anticipated to down-regulate the expression level of OsJMT1 when exogenous synthesized sRNA Xosr001 inoculated on the leaves of OsJMT1-HA-OE transgenic lines. Most notably, the transgenic rice lines OsJMT1-HA-OE exhibited attenuated stomatal immunity and disease susceptibility after ΔXosr001 infection compared with Xoc. These results suggest that Xosr001 packaged in Xoc OMVs highlights a smart molecular mechanism to suppress stomatal immunity in rice.