Systemic elevation of phosphatidic acid and lysophospholipid levels in wounded plants

Plants develop systemic defense responses upon exposure to pathogens or wounding by herbivores. Lipids and lipid metabolites have previously been implicated in induction of defense molecules during plant responses to physical wounding. Possible involvement of changes in lipid composition in systemic wound signal transduction was examined in leaves of seedlings of several different plant species. In the wounded tomato leaf, phosphatidic acid increased approximately fourfold within 5 min whereas lysophosphatidylcholine and lysophosphatidylethanolamine increased over twofold within 15 min of wounding. Similar changes in these lipids were observed in the neighboring non-wounded leaf. In broad bean, soybean, sunflower and pepper seedlings phosphatidic acid levels increased rapidly and systemically upon wounding. The results suggest that the role of phospholipid hydrolysis and accumulation of lipid metabolites in the early events are responsible for systemic wound signal transduction in plants. Furthermore, they indicate that the wound signal propagates outside the wounded leaf within 5 min in these plants.