Liquid-liquid phase separation at the frontline of plant-pathogen battles.

Liquid-liquid phase separation (LLPS) underlies the formation of biomolecular condensates that organize proteins and RNAs without membrane boundaries. In the ongoing arms race between plants and pathogens, LLPS has emerged as a central regulatory mechanism. Pathogens exploit biomolecular condensates to build replication factories or redirect host factors, while plants leverage LLPS to coordinate immune signaling, RNA silencing, and stress adaptation. Recent studies depict a "biomolecular condensate battleground" where the outcome of infection hinges on the dynamic balance between pathogen-induced and host-driven assemblies. In this review, we integrate recent advances in understanding LLPS mediated by viral, fungal, bacterial, and oomycete effectors, along with key host immune regulators. We also discuss the potential of biomolecular condensate engineering as a novel strategy for crop protection and outline the major conceptual and technical challenges that remain. By connecting molecular biophysics with plant pathology, we propose that targeting LLPS offers a timely and promising route for developing durable disease resistance and improving sustainable agricultural productivity.