Suppression of Phospholipase Dγs Confers Increased Aluminum Resistance in Arabidopsis thaliana

Aluminum (Al) toxicity is the major stress in acidic soil that comprises about 50% of the world's arable land. The complex molecular mechanisms of Al toxicity have yet to be fully determined. As a barrier to Al entrance, plant cell membranes play essential roles in plant interaction with Al, and lipid composition and membrane integrity change significantly under Al stress. Here, we show that phospholipase Dγ s (PLDγ s ) are induced by Al stress and contribute to Al-induced membrane lipid alterations. RNAi suppression of PLD γ resulted in a decrease in both PLD γ 1 and PLD γ 2 expression and an increase in Al resistance. Genetic disruption of PLD γ 1 also led to an increased tolerance to Al while knockout of PLD γ 2 did not. Both RNAi-suppressed and pld γ 1-1 mutants displayed better root growth than wild-type under Al stress conditions, and PLD γ 1- deficient plants had less accumulation of callose, less oxidative damage, and less lipid peroxidation compared to wild-type plants. Most phospholipids and glycolipids were altered in response to Al treatment of wild-type plants, whereas fewer changes in lipids occurred in response to Al stress in PLDγ mutant lines. Our results suggest that PLDγs play a role in membrane lipid modulation under Al stress and that high activities of PLDγs negatively modulate plant tolerance to Al.