Phospholipase D Activation Is an Early Component of the Salicylic Acid Signaling Pathway in Arabidopsis Cell Suspensions    

Abstract

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 by PLD is diverted toward the formation of phosphatidylalcohols through a reaction called transphosphatidylation. By in vivo metabolic phospholipid labeling with 33 P i , PLD activity was found to be induced 45 min after addition of SA. We show that incubation of Arabidopsis (Arabidopsis thaliana) cell suspensions with primary alcohols inhibited the induction of two SA-responsive genes, PATHO-GENESIS-RELATED1 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 1,327 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.

SOBER1 phospholipase activity suppresses phosphatidic acid accumulation and plant immunity in response to bacterial effector AvrBsT

“…Arabidopsis contains 12 isoforms partitioned into six classes depending on sequence and biochemical properties (27). Different PLD isoforms are activated by pathogens (28), participate in salicylic acid-dependent signaling (29) and mediate PA-dependent oxidative stress responses (30). Determining which PLD enzymes are involved in AvrBsT triggered immunity should reveal where PA is produced within the plant cell and help to identify which host target(s) and pathways are activated during this interaction.…”

Phospholipases in action during plant defense signaling

“…42 PLDs also participate in salicylic acid-dependent signaling. 43 In contrast, LePLDβ1 is induced after elicitor treatment in tomato and is a negative regulator of ROS production. 44 Similarly, OsPLDβ1-knockdown plants spontaneously activate defense responses, suggesting that OsPLDβ1 would function as a negative regulator of disease resistance.…”

Arabidopsis GLUTATHIONE REDUCTASE1 Plays a Crucial Role in Leaf Responses to Intracellular Hydrogen Peroxide and in Ensuring Appropriate Gene Expression through Both Salicylic Acid and Jasmonic Acid Signaling Pathways

“…evry.inra.fr/projects/FLAGdb++). This array resource has been used in 40 publications over the last 5 years using a protocol based on technical repeats of two independent biological replicates produced from pooled material from independent plants (Achard et al, 2008;Besson-Bard et al, 2009;Krinke et al, 2009), and this approach was adopted in this study. For each biological repeat and each point, RNA samples were obtained by pooling leaf material from independent sets, each of two plants.…”