Extra cellular vesicles as an emerging barrier for phytopathogens

Abstract

Extracellular vesicles (EVs) are spherical, lipid bilayer-bound structures released by both prokaryotic and eukaryotic cells under normal and stress conditions. These vesicles serve as carriers for a wide range of bioactive molecules, including nucleic acids (such as small RNAs and tRNA fragments), proteins (notably defense- and pathogenesis-related), hormones, lipids, and other metabolites. In mammalian systems, EVs are well-established mediators of intercellular communication and are implicated in processes like cancer progression and infectious disease. In contrast, the study of EVs in plants and their associated pathogens is still in its early stages, primarily due to the unique challenges posed by plant cell structures, such as rigid cell walls. However, emerging research reveals that both plants and their microbial pathogens release EVs that play pivotal roles in the dynamics of host-pathogen interactions. Upon detecting pathogens, plants enrich their EVs with small RNAs, pathogenesis-related proteins, and defensive metabolites, which can be taken up by pathogens to silence virulence genes and hinder their growth. Pathogens, in turn, produce EVs loaded with small RNAs, effectors, toxins, and other virulence-associated molecules that can disrupt plant immune responses. While the mechanisms of EV biogenesis and function in plant systems remain incompletely understood, growing evidence supports their role in cross-kingdom communication, influencing both plant defense and pathogen virulence. This review highlights recent advances in our understanding of plant- and pathogen-derived EVs, with a focus on their function in transporting small RNAs and proteins across the host-pathogen interface, their contribution to plant immunity, and their potential as an emerging defense barrier against phytopathogens.