Phospholipase D in hormonal and stress signaling

The phospholipase D (PLD) family are diverse enzymes that are differentially regulated by Ca2+, polyphosphoinositides, free fatty acids, G-proteins, N-acylethanolamines, and membrane lipids. Two new types of PLDs have been identified in the past year: one is activated by oleic acid and the other requires no cation for activity. The oleate-stimulated PLD is associated with the plasma membrane and binds to microtubules. The Ca2+-independent PLD contains a Phox homology (PX) and a pleckstrin homology (PH) domain, but not the Ca2+/phospholipid-binding C2 domain that is found in most plant PLDs. The mechanism by which Ca2+ phosphoinositides, and G proteins regulate certain PLDs is beginning to be understood. PLDs and their product, phosphatidic acid, are involved in various stress responses, including responses to water deficit, salts, wounding, and elicitation. Increasing evidence supports a role for PLD in the abscisic acid signaling cascades.