Submitted to: National Cotton Council Beltwide Cotton Conference
Publication Type: Abstract Only
Publication Acceptance Date: 1/11/1996
Publication Date: N/A
Technical Abstract: Cotton plants respond to infection by Verticillium dahliae by synthesizing a cadalene group of phytoalexins: desoxyhemigossypol (dHG), hemigossypol-6-methyl ether (MHG), and gossypol (G). Early studies established that Z,E-farnesyl diphosphate (FDP) or a steric equivalent such as nerolidyl diphosphate (NDP) is an intermediate in G synthesis. We have isolated a volatile hydrocarbon radiolabelled from [1-3H]-FDP in homogenates of cotton stele tissue infected with V. dahliae. This hydrocarbon was enzymatically labelled from (1R)-[1-2h]-FDP and analyzed by GC-MS. Its mass spectrum agrees with that of delta-cadinene and demonstrates that [5-2H]-delta-cadinene is formed from (1R)-[2H]-FDP and (11-2H)-delta-cadinene is formed from (1S)-[1-2h]-FDP by a proposed mechanism consisting of the isomerization of E,E-FDP to NDP followed by cyclization to a cisgermacradienyl cation and a 1,3-hydride shift, a second cyclization and deprotonation to delta-cadinene.