Hidden Messages in Extracellular Vesicles: Cross-Kingdom RNA Communication in Plant and Microbe Interactions

RNAs are versatile polynucleotides that perform essential functions in coding, regulation, catalysis, and structural organization across all forms of life. While most RNAs function endogenously within an organism, certain RNAs, including small RNAs, messenger RNAs, long noncoding RNAs, and other RNA species, can cross organismal boundaries and regulate cellular processes in recipient organisms, a phenomenon termed "cross-kingdom" or "cross-species" RNA communication. These transferred RNAs play a pivotal role in regulating host-microbe interactions. Extracellular vesicles (EVs) are lipid bilayer-enclosed structures that serve as vehicles for transporting RNAs and other cargoes from donor to recipient cells or organisms to regulate diverse cellular processes. This review summarizes recent advances in our understanding of EVs and their functions in shuttling regulatory molecules, especially RNAs, between hosts and microbes, between hosts and parasites or pests, and even between microbes. Elucidating these mechanisms will enable the development of innovative crop protection strategies.