Nitric oxide and phosphatidic acid crosstalk.

LANTERI, M. L.; DISTÉFANO, A.; TEN HAVE, A.; GARCIA-MATA, C.; LAMATTINA, L.; LAXALT, A.M.

Galveston, Texas, USA.

Congreso; Plant Lipids: Structure, Metabolism & Function; 2009

Gordon Research Conferences

Nitric Oxide (NO) is an important redox based regulator of cell physiology and is involved in many signalling processes in plants. The precise mechanism of how NO interacts with or activates different targets is still poorly understood. NO can activate signalling pathways that implicate cGMP, cADPR, Ca2+, ion channels and protein kinases such as MAPKs and CDPKs. The polar lipid phosphatidic acid (PA) is another molecule involved in plant signalling. Two enzymatic pathways produce PA, phospholipase D (PLD) and phospholipase C (PLC) in concerted action with diacylglycerol kinase (DGK). PA affects ion channels, NADPH oxidase and protein kinases and phosphatases. NO and PA have been independently regarded as general and multifunctional signalling molecules in plants. Since both share common effectors we hypothesized NO and PA participate in the same signalling pathway. Results obtained in our laboratory revealed that NO can induce PA formation during: i) plant-defense responses, ii) stomatal closure and iii) adventitious root formation. i) NO is involved in the plant defense response of a growing list of plant-pathogen interactions. Xylanase is a fungal elicitor that activates a rapid PA production in tomato cells via two enzymatic pathways, PLD and PLC/DGK (van der Luit et al., 2000). NO regulates PA production and subsequent downstream responses via activation of the PLC/DGK pathway, independent of PLD activation (Laxalt et al., 2007). Scavenging of NO or inhibition of either the PLC or the DGK enzyme diminished xylanase-induced ROS production, gene expression and cell death. In order to generalize this crosstalk in plant defense, studies with other elicitors are in progress. ii) NO reduces transpirational water loss by inducing stomatal closure (Garcia-Mata and Lamattina 2001). PLC and PLD activities are required for NO-induced PA formation and stomatal closure in Vicia faba guard cells (Distéfano et al., 2008). Evidences suggest that PLD and PLC are participating in the same signalling pathway. Studies are in progress in order to elucidate which of the PLD enzymes is activated by NO during stomatal closure. iii) Auxin induces a transient increase in the level of NO in the tip of cucumber (Cucumis sativus) hypocotyls, where adventitious roots are formed (Pagnussat et al., 2002). Auxin-induced NO triggers a rapid and transient PA accumulation via PLD activation during adventitious root formation (Lanteri et al., 2008). Accordingly, adventitious root formation was stimulated by treatment with PA and blocked by 1-butanol. The activation of PLC/DGK could not be demonstrated. Auxin also induces an NO-dependent accumulation of PIP and PIP2 by an unknown mechanism. It will be discussed how NO might act on PA-generating enzymes as well as their common downstream effectors like Ca2+, ROS, kinases and phosphatases. Supported by CONICET, ANPCyT and UNMdP.