The AtMYB60 transcription factor regulates stomatal opening by modulating oxylipin synthesis in guard cells
Fabio Simeoni, Aleksandra Skirycz, Laura Simoni, Giulia Castorina, Leonardo Perez de Souza, Alisdair R. Fernie, Saleh Alseekh, Patrick Giavalisco, Lucio Conti, Chiara Tonelli, Massimo Galbiati
Abstract
Stomata are epidermal pores formed by pairs of specialized guard cells, which regulate gas exchanges between the plant and the atmosphere. Modulation of transcription has emerged as an important level of regulation of stomatal activity. The AtMYB60 transcription factor was previously identified as a positive regulator of stomatal opening, although the details of its function remain unknown. Here, we propose a role for AtMYB60 as a negative modulator of oxylipins synthesis in stomata. The atmyb60-1 mutant shows reduced stomatal opening and accumulates increased levels of 12-oxo-phytodienoic acid (12-OPDA), jasmonic acid (JA) and jasmonoyl-L-isoleucine (JA-Ile) in guard cells. We provide evidence that 12-OPDA triggers stomatal closure independently of JA and cooperatively with abscisic acid (ABA) in atmyb60-1. Our study highlights the relevance of oxylipins metabolism in stomatal regulation and indicates AtMYB60 as transcriptional integrator of ABA and oxylipins responses in guard cells.