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Plant Physiology Preview Published on March 20, 2009; 10.1104/pp.108.133595
OPEN ACCESS ARTICLE
Received December 11, 2008 Phospholipase D activation is an early component of the salicylic acid signaling pathway in Arabidopsis thaliana cell suspensions
UPMC Univ Paris 06, Unite de Recherche 5; Centre National de la Recherche Scientifique, Equipe d'Accueil Conventionnee 7180, Laboratoire de Physiologie Cellulaire et Moleculaire des Plantes, Ivry-sur-Seine, F-94200 France; Institute of Chemical Technology, Prague, Department of Biochemistry and Microbiology, Prague, 166 28 Czech Republic; Unite Mixte de Recherche Institut National de la Recherche Agronomique 1165; Centre National de la Recherche Scientifique 8114, Unite de Recherche en Genomique Vegetale, Evry, F-91057 France; Academy of Sciences of the Czech Republic, Institute of Experimental Botany, v.v.i., Prague, 160 00 Czech Republic * Corresponding author; email: eric.ruelland{at}upmc.fr.
Salicylic acid (SA) plays a central role in defense against pathogen attack, as well as in germination, flowering, senescence and the acquisition of thermotolerance. In this report we investigate the involvement of phospholipase D (PLD) in the SA signaling pathway. In presence of exogenous primary alcohols, the production of phosphatidic acid (PA) by PLD is diverted towards the formation of phosphatidylalcohols through a reaction called transphosphatidylation. By in vivo metabolic phospholipid labeling with 33Pi, PLD activity was found to be induced 45 min after addition of SA. We show that incubation of Arabidopsis thaliana cell suspensions with primary alcohols inhibited the induction of two SA-responsive genes, PR1 and WRKY38, in a dose dependent manner. This inhibitory effect was more pronounced when the primary alcohols were more hydrophobic. Secondary or tertiary alcohols had no inhibitory effect. These results provide compelling arguments for PLD activity being upstream of the induction of these genes by SA. A subsequent study of n-butanol effects on the SA responsive transcriptome identified 1327 genes differentially expressed upon SA treatment. Strikingly, the SA-response of 380 of these genes was inhibited by n-butanol but not by tert-butanol. A detailed analysis of the regulation of these genes showed that PLD could act both positively and negatively, either on gene induction or gene repression. The overlap with the previously described Phosphatidylinositol-4-Kinase pathway is discussed.
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