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United States Department of Agriculture

Agricultural Research Service

Title: The Biochemistry of Gossypol Formation in Cotton Plants: Delta-Cadinene Synthase

item Benedict, C - TEXAS A&M UNIVERSITY
item Alchanati, I - TEXAS A&M UNIVERSITY
item Stipanovic, Robert
item Bell, Alois

Submitted to: National Cotton Council Beltwide Cotton Conference
Publication Type: Abstract Only
Publication Acceptance Date: January 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.

Last Modified: 4/18/2015