Osmotic stress-triggered stomatal closure requires Phospholipase Dδ and hydrogen sulfide in Arabidopsis thaliana.

Osmotic stress is one of the main stresses seriously affects the growth and development of plants. Hydrogen sulfide (HS) emerges as the third gaseous signal molecule to involve in the complex network of signaling events. Phospholipase Dδ (PLDδ), as signal enzyme, responds to many biotic or abiotic stress responses. In this study, the functions and the relationship of PLDδ and HS in stomatal closure induced by osmotic stress were explored. Using the seedlings of ecotype (WT), PLDδ deficient mutant (pldδ), L-cysteine desulfhydrase (LCD) deficient mutant (lcd) and pldδlcd double mutant as materials, the Real-time quantitative PCR (RT-qPCR) and the stomatal aperture were analyzed. Osmotic stress induced the expressions of PLDδ and LCD. The HS content and the activities of PLD and LCD ascended in WT under osmotic stress. The phenotypes of pldδ, lcd and pldδlcd were more sensitive to osmotic stress than WT. Compared with pldδ, the stomatal of lcd showed lower sensitivity to osmotic stress, and the stomatal aperture of pldδlcd was similar to that of lcd. Simultaneous application of PA and NaHS resulted in tighter closure of stomatal than application of either PA or NaHS alone. These results suggested that osmotic stress-triggered stomatal closure requires PLDδ and HS in A. thaliana. LCD acted downstream of PLDδ to regulate the stomatal closure induced by osmotic stress.