MpDGK2, a Novel Diacylglycerol Kinase from Malus prunifolia , Confers Drought Stress Tolerance in Transgenic Arabidopsis

Phospholipase D (PLD)– and phospholipase C (PLC)/diacylglycerol kinase (DGK)–coupled pathways produce phosphatidic acid (PA), which is an important signal transduction process in animal and plant cells. DGK is the second largest PA-generating factor after PLD in both biotic and abiotic stress responses, which could phosphorylate diacylglycerol (DG) to form PA. Here, we assessed the biological role of MpDGK2 , a DGK gene isolated from Malus prunifolia that is upregulated by water deficit, oxidation, or exogenous abscisic acid. Its heterotopic expression is helpful to improve the drought resistance of transgenic Arabidopsis thaliana . Changes in electrolyte leakage, chlorophyll concentration, and malondialdehyde accumulation showed a positive response. MpDGK2 had effect on stomatal closure under water withholding condition. In addition, under stress conditions, MpDGK2 significantly regulates the accumulation of hydrogen peroxide (H 2 O 2 ), which is manifested in the fluctuation of H 2 O 2 concentration and the change of antioxidant enzyme activity. In summary, these results indicate that MpDGK2 affects the growth and tolerance of Arabidopsis under drought stress. Part of its function may be due to its effects on stomatal behavior and reactive oxygen species accumulation, thereby improving drought tolerance.