QUANTITATION OF THE OCTADECANOID 12-OXO-PHYTODIENOIC ACID, A SIGNALING COMPOUND IN PLANT MECHANOTRANSDUCTION

The octadecanoid 12-oxo-phytodienoic acid (OPDA) is an intermediate in biosynthesis of jasmonic acid in plants. A technique for the quantita tion of this compound is described which has a limit of detection of 2 0 pg cis-OPDA corresponding to 4 ng g(-1) tissue for the overall proce dure and which uses high isotopic abundance [H-2(5)]cis-(+/-)-OPDA, sy nthesized enzymatically by recombinant allene oxide synthase, as inter nal standard. The levers of cis-OPDA have been determined in a wide va riety of monocotyledonous and dicotyledonous angiosperms and were foun d to vary considerably among different species. In mechanically stimul ated tendrils of Bryonia dioica, the level of cis-OPDA increases sever al-fold, correlating with the initiation and progression of the free c oiling response. In Phaseolus vulgaris internodes undergoing a thigmom orphogenic response, the levels of cis-OPDA were also found to increas e several-fold well before the development of thigmomorphogenic sympto ms. The thigmomorphogenic reaction could also be triggered by applicat ion of the octadecanoid structural analog, coronatine. Coronatine did not induce OPDA accumulation in treated tissues and is thus active per se. In both species, Bryonia dioica and Phaseolus vulgaris, the (+)-e nantiomer of cis-OPDA is found and accumulates after mechanical stimul ation. Our results establish 12-oxo-phytodienoic acid as a signalling compound in higher plant mechanotransduction. (C) 1997 Elsevier Scienc e Ltd. All rights reserved.