PARTIAL SEQUENCE COMPARISON BETWEEN TAXADIENE SYNTHASE cDNA CLONES OF TAXUS BREVIFOLIA AND T. MAIREI

¹ Dept. of Biology, Virginia Commonwealth University, Richmond, VA 23284-2012 USA

² Genetics Research Center, National Chung-Hsin University, Taichung, Taiwan

³ Division of Silviculture, Taiwan Forestry Research, Institute Taipei, Taiwan

Taxadiene synthase is an enzyme that catalyzes the first committed cyclization step of geranylgeranyl diphospate to taxa-4(5),11(12)-diene, leading to a complicated biosynthesis pathway of taxol production. The diterpenoid taxol is a very effective anticancer drug, and has been isolated almost exclusively from the T. brevifolia, a slow growing pacific yew shrub. The T. mairei, a 5-10 m in diameter giant tree found in the high mountains of Taiwan, also produces high amounts of taxol and its related compounds. We have isolated RNA from young needles of embryo-derived in vitro plantlets of T. mairei, and employed reverse polymerase chain reactions to synthesize the cDNA of taxadiene synthase gene. DNA primers based on the cDNA sequence of taxadiene synthase from T. brevifolia were used in the polymerase chain reactions. Several DNA fragments were produced and cloned. The partial sequencing of a 1.66 kb cDNA clone revealed that there is a 94% similarity between the sequences of the taxadiene synthase gene from T. mairei and T. brevifolia. The cDNA clone could be used to facilitate studies for the regulation of gene expression of the taxadiene synthase, particularly under conditions that could stimulate the biosynthesis of taxol in the cell culture of T. mairei.