Plant exosomes mediate cross-kingdom RNA interference ($) (Science)

Small RNAs (sRNAs) trafficking between host plant and pathogens can occur in a wide range on interactions. Pathogen-produced sRNAs have been shown to suppress host plant immunity, and conversely host plant-derived sRNAs can reduce pathogen virulence by targeting pathogenic genes of the pest. Nevertheless, mechanisms ensuring host/pest sRNAs transfer remain unclear. In this study, Cai et al. used the Arabidopsis/Botrytis cinerea pathosystem to identify the molecular vehicle responsible for directional plant sRNA exchange. They first confirm that plant endogenous sRNAs are not only transferred into the fungus, but supress fungal pathogenicity by silencing virulence genes. They further show that plant sRNAs accumulate into exosome-like extracellular vesicles secreted by Arabidopsis cells at infection sites, and later detected in the fungal cells where they are believed to deliver the sRNAs targeting virulence genes. Together, this study describes plant exosomes as the molecular vehicle mediating plant-pathogen sRNAs trafficking, and offers new perspectives in plant disease control. (Summary by Matthias Benoit) Science 10.1126/science.aar4142