Extracellular Vesicles: Key Mediators of Bioactive Molecule Transport in Plant-Microbe Interactions.

Extracellular vesicles (EVs) are nanoscale, lipid-bilayer particles released by cells, which transport a diverse array of bioactive cargo such as nucleic acids, proteins, lipids, and metabolites. There is growing evidence that EVs act as important mediators in the bidirectional exchange of biomolecules between plants and microbes, thereby playing essential roles in their interactions. Plant-derived EVs can deliver defence-related nucleic acids and proteins to fungal pathogens, suppressing their virulence. Conversely, microbial EVs transport virulence factors, such as pathogenicity-related nucleic acids and proteins, into plant cells to promote infection. Despite recent advancements, research into the functions of plant EVs continues to lag significantly behind that of animal systems. This review begins by summarizing the role of EVs in facilitating cross-kingdom communication through the transport of bioactive molecules between plants and microorganisms, a process crucial for plant-microbe interactions. We highlight emerging evidence and potential mechanisms of EVs in establishing beneficial symbioses. Subsequently, we explore the putative functions of EVs in the systemic transmission of immune signals within plants. Finally, we propose future research directions based on current knowledge. By synthesizing these insights, this review serves as a timely and comprehensive resource to facilitate future functional studies on EVs in the interface of plant-microbe interactions.