PHOSPHOLIPASE-ACTIVITY AND PHOSPHOLIPID PATTERNS IN TOBACCO CELLS TREATED WITH FUNGAL ELICITOR

In relation to previous findings that lipoxygenase is induced in tobacco treated with elicitors of Phytophthora parasitica var. nicotianae, a fungal pathogen of this plant, we analyzed phospholipid changes and phospholipase A activity in elicitor-treated tobacco cells. It was found that phosphatidylcholine and phosphatidylethanolamine are the main phospholipids of tobacco cell membranes, and that linoleic and linolenic acids, two potential lipoxygenase substrates, represent 58.7% and 12.1%, respectively, of the total fatty acid content of the cells. Time course studies showed that the amount of phosphatidylcholine was reduced in response to elicitors and that a concomitant increase of phospholipase A activity occurred. Phospholipase induction was dose-dependent and required protein synthesis. Our data suggest that phospholipase induction could be one of the first steps of the lipoxygenase pathway of jasmonic acid biosynthesis leading to defence in elicitor-treated tobacco cells.