Stomatal Movement Examination: A New Model to Reveal Interactions Between Grapevine and Phaeomoniella chlamydospora, an Esca-Associated Pathogen

Esca is a complex and poorly understood trunk disease which causes important economic losses in vineyards. Genetic solution or biostimulation are the main approaches being considered to achieve vineyard protection. Thus, the characterization of molecular events occurring throughout the first steps of the interactions between grapevine cells and Esca-associated pathogens is a prerequisite, but impossible to perform directly in the grapevine trunk. To achieve this future goal, we have developed an innovative strategy based on aperture of stomata (specialized structures consisting of two guard cells surrounding a pore) to study and describe plant cell response to esca-associated pathogens. Guard cells, which serve as a model for studying cell signaling, perceive environmental stimuli and regulate stomatal aperture through opening and closing, a process that can be quantitatively assessed. Assays on epidermal peels reveal that mycelium or cell wall fragments from Phaeomoniella chlamydospora (Pch, one of the main esca-associated pathogens) induced stomatal closure in Vitis vinifera and Arabidopsis thaliana plants. In addition, the use of 1-methylcyclopropene, a competitive inhibitor of ethylene, partially blocked the stomatal closure in response to Pch, suggesting an involvement of the ethylene cell signaling in grapevine response to this pathogen. Moreover, we observed that an extract of extracellular compounds from Pch induced stomatal opening. Overall results showed that, guard cells and stomatal responses are efficient and promising tools to establish a cell pathosystem model to characterize and explore molecular events that occur during interactions between grapevine and esca-associated pathogens.