In vivo substrates and the contribution of the common phospholipase D, PLDα, to wound-induced metabolism of lipids in Arabidopsis

The common plant phospholipase D (PLD), PLD alpha, has been proposed to be involved in wound-induced production of jasmonic acid. To better understand the role(s) of PLD alpha in the wound response, detailed lipid analysis was carried out to determine the in vivo substrates and the contribution of PLDa in wound-induced lipid metabolism in Arabidopsis thaliana. Mechanical wounding of Arabidopsis leaves resulted in significantly less hydrolysis of phosphatidylcholine (PC) in PLD alpha -deficient than in wild-type plants. Hydrolysis of phosphatidylethanolamine, phosphatidylglycerol (PG), and phosphatidylinositol within 30 min of wounding was not significantly different in PLD alpha -deficient and wild-type leaves. Phosphatidic acid (PA) levels increased rapidly in wild-type and, to a lesser extent, in PLD alpha -deficient plants. The acyl composition of the PA generated by wounding suggests that the major in vivo substrate of PLD in wild-type leaves was PC, and that PG hydrolysis accounted for 10-15% of the wound-induced PA in wild-type leaves. Comparison of the acyl compositions of the wound-induced PA of wild-type and PLD alpha -deficient leaves indicated that PLD alpha hydrolyzed PG more readily than other PLD isoforms did. Wounding produced substantial increases in free linoleic and linolenic acids in wild-type plants, whereas PLD alpha -deficient plants showed only a slight increase in linoleic acid and no significant increase in linolenic acid. These results demonstrate that PLD alpha and at least one other PLD isoform, as well as other hydrolytic enzymes, are active in mechanically wounded Arabidopsis leaves, and PLD alpha is involved in wound-induced metabolism of polyunsaturated fatty acids. (C) 2001 Elsevier Science B.V. All rights reserved.