(+)-δ-Cadinene is a product of sesquiterpene cyclase activity in cotton

Abstract

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- 3H]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. malvacearum converted nonradioactive ( E, E)-farnesyl pyrophosphate into the hydrocarbon product, which was identified as (+)-δ-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 [ 3H] (+)-δ-cadinene into previously inoculated glandless cotton cotyledons. The accumulation of (+)-δ-cadinene in bacteria-inoculated or elicitor-treated cotton cotyledons and the results of the incorporation experiment suggest that (+)-δ-cadinene is an early enzymatic intermediate in the biosynthesis of the sesquiterpenoid phytoalexins by upland cotton.