Cross-stress memory in plants: mobile RNAs, extracellular vesicles, and local-to-systemic signal integration.

Plants rarely experience environmental stresses as isolated events. Instead, they are exposed to recurring, overlapping, or sequential challenges that require not only immediate local responses but also coordinated systemic adaptation and memory. Although plant stress memory has traditionally been discussed in terms of transcriptional, epigenetic, and metabolic reprogramming, accumulating evidence suggests that long-distance communication is equally important in determining how prior stress exposure shapes future responses. In this context, mobile RNAs and extracellular vesicles (EVs) are emerging as key mediators of local-to-systemic information transfer. Mobile RNAs, including small RNAs, mRNAs, long non-coding RNAs, and related RNA species, can move across cells, tissues, organs, and even species boundaries to regulate stress adaptation, whereas plant EVs carry complex molecular cargoes that participate in intercellular signalling, defense, and stress-responsive communication. Recent studies further indicate that EV secretion is stress-inducible and that plant EVs can amplify immune signalling during systemic acquired resistance (SAR), highlighting their potential contribution to plant-wide memory-like states. This review proposes that cross-stress memory should be reconsidered as a systemic signaling phenomenon, in which local stress encounters generate transmissible molecular information that reshapes distal tissue responsiveness and influences later reactions to the same or different stresses. We synthesize current knowledge on plant stress memory, RNA mobility, EV biogenesis and cargo, and systemic signalling networks, with emphasis on how these components may converge to establish, propagate, and recall stress information across the plant body. By linking mobile RNAs and EV-mediated communication with recurrent and cross-stress acclimation, this review provides a new conceptual framework for plant stress tolerance and identifies experimental priorities and translational opportunities for crop resilience under dynamic environments.