(+)-DELTA-CADINENE IS A PRODUCT OF SESQUITERPENE CYCLASE ACTIVITY IN COTTON

Glandless cotton cotyledons stimulated to produce sesquiterpenoid phytoalexins by inoculation with Xanthomonas campestris pv. malvacearum, or by injection of oligogalacturonide elicitors, generated a hydrocarbon that was absent in mock-inoculated or non-inoculated cotyledons. Enzyme preparations from the same cotton cotyledons catalysed cell-free reactions which converted (E,E)-[1-H-3]farnesyl pyrophosphate into a predominant tritium-labelled hydrocarbon product. Large-scale cell-free reactions catalysed by enzyme preparations from cotton cotyledons previously inoculated with Xanthomonas campestris pv. maluacearum converted nonradioactive (E,E)-farnesyl pyrophosphate into the hydrocarbon product, which was identified as (+)-delta-cadinene by chiral GC-mass spectrometry. In planta incorporation of tritium into the sesquiterpenoid phytoalexins 2,7-dihydroxycadalene, lacinilene C, lacinilene C7-methyl ether and structurally related terpenoids occurred following injection of [H-3](+)-delta-cadinene into previously inoculated glandless cotton cotyledons. The accumulation of (+)-delta-cadinene in bacteria-inoculated or elicitor-treated cotton cotyledons and the results of the incorporation experiment suggest that (+)-delta-cadinene is an early enzymatic intermediate in the biosynthesis of the sesquiterpenoid phytoalexins by upland cotton.