Phospholipase A2β mediates light-induced stomatal opening in Arabidopsis

Abstract

Phospholipase A₂ (PLA₂) catalyses the hydrolysis of phospholipids into lysophospholipids and free fatty acids. Physiological studies have indicated that PLA₂ is involved in stomatal movement. However, genetic evidence of a role of PLA₂ in guard cell signalling has not yet been reported. To identify PLA₂ gene(s) that is (are) involved in light-induced stomatal opening, stomatal movement was examined in Arabidopsis thaliana plants in which the expression of PLA₂ isoforms was reduced or knocked-out. Light-induced stomatal opening in PLA₂α knockout plants did not differ from wild-type plants. Plants in which PLA₂β was silenced by RNA interference exhibited delayed light-induced stomatal opening, and this phenotype was reversed by exogenous lysophospholipids, which are products of PLA₂. Stomatal opening in transgenic plants that over-expressed PLA₂β was faster than wild-type plants. The expression of PLA₂β 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 PLA₂β. Collectively, these results provide evidence that PLA₂β is involved in light-induced stomatal opening in Arabidopsis.