Populus euphratica Phospholipase Dδ Increases Salt Tolerance by Regulating K + /Na + and ROS Homeostasis in Arabidopsis.

Phospholipase Dα (PLDα), which produces signaling molecules phosphatidic acid (PA), has been shown to play a critical role in plants adapting to salt environments. However, it is unclear whether phospholipase Dδ (PLDδ) can mediate the salt response in higher plants. PePLDδ was isolated from salt-resistant Populus euphratica and transferred to Arabidopsis thaliana to testify the salt tolerance of transgenic plants. The NaCl treatment (130 mM) reduced the root growth and whole-plant fresh weight of wild-type (WT) A. thaliana , vector controls (VC) and PePLDδ -overexpressed lines, although a less pronounced effect was observed in transgenic plants. Under salt treatment, PePLDδ -transgenic Arabidopsis exhibited lower electrolyte leakage, malondialdehyde content and H 2 O 2 levels than WT and VC, resulting from the activated antioxidant enzymes and upregulated transcripts of genes encoding superoxide dismutase, ascorbic acid peroxidase and peroxidase. In addition, PePLDδ -overexpressed plants increased the transcription of genes encoding the plasma membrane Na + /H + antiporter ( AtSOS1 ) and H + -ATPase ( AtAHA2 ), which enabled transgenic plants to proceed with Na + extrusion and reduce K + loss under salinity. The capacity to regulate reactive oxygen species (ROS) and K + /Na + homeostasis was associated with the abundance of specific PA species in plants overexpressing PePLDδ . PePLDδ -transgenic plants retained a typically higher abundance of PA species, 34:2 (16:0-18:2), 34:3 (16:0-18:3), 36:4 (18:2-18:2), 36:5 (18:2-18:3) and 36:6 (18:3-18:3), under control and saline conditions. It is noteworthy that PA species 34:2 (16:0-18:2), 34:3 (16:0-18:3), 36:4 (18:2-18:2) and 36:5 (18:2-18:3) markedly increased in response to NaCl in transgenic plants. In conclusion, we suppose that PePLDδ -derived PA enhanced the salinity tolerance by regulating ROS and K + /Na + homeostasis in Arabidopsis.