Alleviation of osmotic stress by H2S is related to regulated PLDα1 and suppressed ROS in Arabidopsis thaliana.

Hydrogen sulfide (H₂S) is an important gaseous molecule responding to osmotic stress in plant. Phospholipase Dα1 (PLDα1) and reactive oxygen species (ROS) are involved in many biotic or abiotic stress responses. Using the seedlings of Arabidopsis thaliana ecotype (WT), PLDα1 deficient mutant (pldα1) and the L-cysteine desulfhydrase (L-DEs) deficient mutant (lcd) as materials, the effect of H₂S responding to osmotic stress and the functions of PLDα1 and ROS in this response were investigated. The results showed that H₂S, PLDα1 and ROS were involved in osmotic stress resistance. Exogenous sodium hydrosulfide (NaHS) promoted the endogenous H₂S content and up-regulated the expression of LCD in WT, lcd and plda1. Exogenous phosphatidic acid (PA) enhanced the H₂S content and up-regulated the expressions of LCD in WT and plda1 but had no significant effect on the H₂S content and LCD expression in lcd under osmotic stress. This suggested that H₂S was located downstream of PLDα1 to participate in the osmotic stress signal response. Exogenous NaHS treatment regulated the antioxidant enzymes (SOD, POD, and CAT). The activities and the gene relative expressions of antioxidant enzymes in pldα1 and lcd were higher than those in WT under osmotic stress. This indicated that H₂S and PLD regulated the antioxidant enzyme system under osmotic stress. The ROS level, electrolyte leakage (EL), malondialdehyde (MDA) were decreased by NaHS under osmotic stress, demonstrating H₂S maintained the membrane integrity. All of these results revealed that H₂S alleviated the osmotic stress by elevating PLD and suppressing ROS in A. thaliana.