Biosynthesis of the Diterpene cis-Abienol in Cell-Free Extracts of Tobacco Trichomes

Biosynthesis of the hydroxylated labdane diterpene, cis-abienol, 9αH-[(12Z)-labda-12,14-dien-8α-ol] from geranylgeranyl pyrophosphate was observed in cell-free extracts prepared from trichome-bearing tissues of the experimental tobacco, Nicotiana tabacum L. c.v. T.I. 1068. Synthetic activity was observed with extracts of trichome glands, but not subepidermal tissue or epidermis from which glands had been removed. The activity was soluble, Mg2+ stimulated, had a pH optimum near 7.0, and was unaffected by conditions which inhibit cytochrome P450 oxygenase. These results indicate the occurrence in trichome glands of T.I. 1068, a cyclase activity which yields the cyclized hydroxylated labdanoid cis-abienol directly.