Phospholipase A2β mediates light-induced stomatal opening in Arabidopsis

Phospholipase A(2) (PLA(2)) catalyses the hydrolysis of phospholipids into lysophospholipids and free fatty acids. Physiological studies have indicated that PLA(2) is involved in stomatal movement. However, genetic evidence of a role of PLA(2) in guard cell signalling has not yet been reported. To identify PLA(2) gene(s) that is (are) involved in light-induced stomatal opening, stomatal movement was examined in Arabidopsis thaliana plants in which the expression of PLA(2) isoforms was reduced or knocked-out. Light-induced stomatal opening in PLA(2)alpha knockout plants did not differ from wild-type plants. Plants in which PLA(2)beta was silenced by RNA interference exhibited delayed light-induced stomatal opening, and this phenotype was reversed by exogenous lysophospholipids, which are products of PLA(2). Stomatal opening in transgenic plants that over-expressed PLA(2)beta was faster than wild-type plants. The expression of PLA(2)beta was localized to the endoplasmic reticulum of guard cells, and increased in response to light in the mature leaf. Aristolochic acid, which inhibits light-induced stomatal opening, inhibited the activity of purified PLA(2)beta. Collectively, these results provide evidence that PLA(2)beta is involved in light-induced stomatal opening in Arabidopsis.