Phospholipases D (PLD) and C (PLC) hydrolyze the phosphodiesteric linkages of the head group of membrane phospholipids. PLDs and PLCs in plants occur in different forms: the calcium-dependent phospholipid binding domain-containing PLDs (C2-PLDs), the plekstrin homology and phox homology domain-containing PLDs (PX/PH-PLDs), phosphoinositide-specific PLC (PI-PLC), and non-specific PLC (NPC). They differ in structures, substrate selectivities, cofactor requirements, and/or reaction conditions. These enzymes and their reaction products, such as phosphatidic acid (PA), diacylglycerol (DAG), and inositol polyphosphates, play important, multifaceted roles in plant response to abiotic and biotic stresses. Here, we review biochemical properties, cellular effects, and physiological functions of PLDs and PLCs, particularly in the context of their roles in stress response along with advances made on the role of PA and DAG in cell signaling in plants. The mechanism of actions, including those common and distinguishable among different PLDs and PLCs, will also be discussed.

Reactive oxygen species (ROS) are produced in plants under various stress conditions and serve as important mediators in plant responses to stresses. Here, we show that the cytosolic glycolytic enzymes glyceraldehyde-3-phosphate dehydrogenases (GAPCs) interact with the plasma membrane-associated phospholipase D (PLDd) to transduce the ROS hydrogen peroxide (H 2 O 2 ) signal in Arabidopsis thaliana. Genetic ablation of PLDd impeded stomatal response to abscisic acid (ABA) and H 2 O 2 , placing PLDd downstream of H 2 O 2 in mediating ABA-induced stomatal closure. To determine the molecular link between H 2 O 2 and PLDd, GAPC1 and GAPC2 were identified to bind to PLDd, and the interaction was demonstrated by coprecipitation using proteins expressed in Escherichia coli and yeast, surface plasmon resonance, and bimolecular fluorescence complementation. H 2 O 2 promoted the GAPC-PLDd interaction and PLDd activity. Knockout of GAPCs decreased ABA-and H 2 O 2 -induced activation of PLD and stomatal sensitivity to ABA. The loss of GAPCs or PLDd rendered plants less responsive to water deficits than the wild type. The results indicate that the H 2 O 2 -promoted interaction of GAPC and PLDd may provide a direct connection between membrane lipid-based signaling, energy metabolism and growth control in the plant response to ROS and water stress.