Nitric Oxide and Phosphatidic Acid Signaling in Plants

Nitric oxide (NO) is an important redox-based regulator of cell physiology involved in many signaling processes in plants. The precise mechanism of how NO activates or interacts with different targets is still poorly understood. The polar lipid, phosphatidic acid (PA) is another molecule involved in plant signaling. NO and PA have been independently regarded as general, multifunctional, stress-signaling molecules in plants. Since they share common effectors, we hypothesized that NO and PA participate in the same signaling pathways. Results from our laboratory revealed that NO can induce PA formation during (1) plant-defense responses, (2) stomatal closure, and (3) adventitious root formation. Two enzymatic pathways produce PA, phospholipase D, and phospholipase C in concerted action with the diacylglycerol kinase. We discuss how NO might act on PA-generating enzymes as well as on their common downstream effectors such as Ca2+, reactive oxygen species, protein kinases, and phosphatases.