Investigating the Role of AtPIEZO as a Possible Mechanoreceptor During Plant Defense

Plants are capable of perceiving and responding to biotic and abiotic stress. They have evolved a variety of mechanisms to help them recognize and trigger rapid responses to both chemical and mechanical stimuli. These signals coordinate plant growth, development, and innate immune responses. However, we have limited knowledge about how mechanical signals are perceived and transduced during the plant immune response. In this study, we investigated the potential role of PIEZO, a mechanosensitive ion channel that is responsible for cellular mechanotransduction in both the plant and animal kingdoms, during the plant immune responses. Publicly- available RNAseq data revealed that PIEZO expression remained constant and unaltered in response to a variety of phytopathogens or elicitors. We, then, conducted infectious growth assays on piezo mutants in Arabidopsis thaliana plants. Our results indicated that piezo mutants, pzo1-1 and pzo1-5, were more susceptible to Pseudomonas syringae pv. tomato (Pst) DC3000 and to the P. syringae hrcC^- mutant confirming PIEZO’s role in plant defense and PTI. We further explored disease progression with necrotrophic fungi, Alternaria brassisicola and Botrytis cinerea, on piezo mutant plants and found enhanced fungal growth compared to the wild type (Col-0) with Botrytis. Building upon these findings, we probed the role of PIEZO in the growth-defense tradeoff using a root growth inhibition assay with flg22 as the MAMP elicitor. pzo1-1 was less sensitive to flg22 treatment with less reduction in root growth compared to wild type whereas pzo1-5 shows no difference in reduction compared to Col-0. In addition, we investigated whether PIEZO operates upstream of the main NADPH-oxidase, RBOHD, and the associated oxidative burst that occurs in early defense. There was no significant difference in Reactive Oxygen Species (ROS) production between piezo mutants and the wild type in an apoplastic ROS assay with a MAMP elicitor (flg22) and also with Ca²⁺ flux leaf disk assay. In conclusion, we demonstrated a potential role for PIEZO in plant immune defense responses and the growth-defense tradeoff.