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Phospholipase D3 Is Involved in the Hyperosmotic Response in Arabidopsis

^a Department of Biology, University of Missouri, St. Louis, Missouri 63121
^b Donald Danforth Plant Science Center, St. Louis, Missouri 63132
^c Kansas Lipidomics Research Center, Division of Biology, Kansas State University, Manhattan, Kansas 66506

¹ Address correspondence to wangxue{at}umsl.edu.

Rapid activation of phospholipase D (PLD), which hydrolyzes membrane lipids to generate phosphatidic acid (PA), occurs under various hyperosmotic conditions, including salinity and water deficiency. The Arabidopsis thaliana PLD family has 12 members, and the function of PLD activation in hyperosmotic stress responses has remained elusive. Here, we show that knockout (KO) and overexpression (OE) of previously uncharacterized PLD3 alter plant response to salinity and water deficit. PLD3 uses multiple phospholipids as substrates with distinguishable preferences, and alterations of PLD3 result in changes in PA level and membrane lipid composition. PLD3-KO plants display increased sensitivities to salinity and water deficiency and also tend to induce abscisic acid–responsive genes more readily than wild-type plants, whereas PLD3-OE plants have decreased sensitivities. In addition, PLD3-KO plants flower later than wild-type plants in slightly dry conditions, whereas PLD3-OE plants flower earlier. These data suggest that PLD3 positively mediates plant responses to hyperosmotic stresses and that increased PLD3 expression and associated lipid changes promote root growth, flowering, and stress avoidance.