Professor Universite de Sherbrooke Sherbrooke, Quebec, Canada
Numerous plant pathogens divergently evolved virulence strategies converging on inducing a water-soaked niche in the extracellular space (the apoplast) of their host to cause disease. Here, we show that extracellular water content is the rate-limiting step for compatible and incompatible plant-pathogen interactions. Genetic and hyperspectral imaging analysis reveal that the plant hypersensitive response caused by the activation of effector-triggered immunity (ETI) is the result of a desiccation of plant tissues. Mutant plants displaying spontaneous water-soaking or extracellular water complementation during ETI elicitation abrogates immune protection against a bacterial pathogen despite cell death occurring. ETI induces a stasis-like state in bacterial pathogens, effectively halting pathogenesis rather than eliminating the bacteria, by dehydrating the apoplast. Pathogenesis can be reinitiated upon rehydration of the extracellular space. These results highlight the pivotal role of extracellular water in modulating plant immune responses, illustrating how water content within the apoplast disrupts both cell-surface and intracellular execution of immunity, without affecting the signaling cascade.
