RNA ‘Information Warfare’ in Pathogenic and Mutualistic Interactions

Regulatory non-coding RNAs are emerging as key players in host–pathogen interactions. Small RNAs such as microRNAs are implicated in regulating plant transcripts involved in immunity and defence. Surprisingly, RNAs with silencing properties can be translocated from plant hosts to various invading pathogens and pests. Small RNAs are now confirmed virulence factors, with the first report of fungal RNAs that travel to host cells and hijack post-transcriptional regulatory machinery to suppress host defence. Here, we argue that trans-organism movement of RNAs represents a common mechanism of control in diverse interactions between plants and other eukaryotes. We suggest that extracellular vesicles are the key to such RNA movement events. Plant pathosystems serve as excellent experimental models to dissect RNA ‘information warfare’ and other RNA-mediated interactions.

TrendsPlant–pathogen interactions have undergone a paradigm shift, with the observation that silencing, non-coding RNAs move between host and pathogen, and vice versa.So far, only one unequivocal natural example of this phenomenon has been exposed, where RNAs from Botrytis cinerea (grey mould) move into host plants. There, they ‘hijack’ host silencing machinery to downregulate transcripts involved in defence and immunity.Similar RNA-based phenomena in interactions between animals and their microbial pathogens suggest that this mechanism is a commonality between infections in widely divergent taxa.As well as a potent tool for developing new crops with increased disease resistance, studies of RNA traffic between plants and their symbionts will serve as models for other disease interactions.