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 D gamma s (PLD gamma s) are induced by Al stress and contribute to Al-induced membrane lipid alterations. RNAi suppression of PLD gamma resulted in a decrease in both PLD gamma 1 and PLD gamma 2 expression and an increase in Al resistance. Genetic disruption of PLD gamma 1 also led to an increased tolerance to Al while knockout of PLD gamma 2 did not. Both RNAi-suppressed and pld gamma 1-1 mutants displayed better root growth than wild-type under Al stress conditions, and PLD gamma 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 PLD gamma mutant lines. Our results suggest that PLD gamma s play a role in membrane lipid modulation under Al stress and that high activities of PLD gamma s negatively modulate plant tolerance to Al.