A rapid response to a plant hormone: auxin stimulates phospholipase A2 in vivo and in vitro.

Addition of the active auxins indole-3-acetic acid, 2,4-dichlorophenoxyacetic acid or alpha-naphthylacetic acid to cultured soybean (Glycine max L.) cells prelabeled with ethanolamine or choline increased the radioactivity in the lysophosphatidylethanolamine (LPE) or lysophosphatidylcholine (LPC) pool within 5 min. The inactive auxin analogue, beta-naphthylacetic acid, was inactive in this response. In membranes prelabeled in vivo, either with ethanolamine or choline, and subsequently isolated from zucchini (Cucurbita pepo L.) hypocotyls, indole-3-acetic acid and 2,4-dichlorophenoxyacetic acid stimulated the conversion of phosphatidylethanolamine (PE) to LPE and of phosphatidylcholine (PC) to LPC in vitro whereas the inactive auxin analogue 2,3-dichlorophenoxyacetic acid did not.