title: Stimulation by auxin of phospholipase A in membrane vesicles from an auxin-sensitive tissue is mediated by an auxin receptor.
abstract: Microsomal vesicles were prepared from zucchini (Cucurbita pepo L.) hypocotyls containing radioactive phosphatidylethanolamine or phosphatidylcholine, and these lipids were used as substrates by phospholipase A which is activated by auxins. Phospholipase D and phospholipase C hydrolysed the same substrates but were not influenced by auxin. Phospholipase A was activated by the auxins indolyl-3-acetic acid, 2,4-dichlorophenoxyacetic acid and, to a lesser extent, by α-naphthaleneacetic acid whereas the weak auxins 2,3-dichlorophenoxyacetic acid and β-naphthaleneacetic acid were almost inactive. This hormone specificity was also found in growth tests with etiolated zucchini hypocotyls. Phospholipase A activation by auxin was blocked by a polyclonal antibody against the maize auxin-binding protein. We propose that phospholipase A activation is a primary reaction in the signal transduction leading from hormone-binding to the growth response.
authors.affiliation: Botanisches Institut, Universität Bonn, Venusbergweg 22, 1, Bonn, Germany.
authors.forename: B
authors.initials: B
authors.lastname: André
authors.forename: G F
authors.initials: GF
authors.lastname: Scherer