Abstract
Taxus spp. is a highly valuable medicinal plant with multiple pharmacological effects on various cancers. Cytochrome P450s (CYP450s) play important roles in the biosynthesis of active compounds in Taxus spp., such as the famous diterpenoid, Taxol. However, some specific CYP450 enzymes involved in the biosynthesis of Taxol remain unknown, and the systematic identification of CYP450s in Taxus has not been reported. In this study, 118 full-length and 175 partial CYP450 genes were identified in Taxus chinensis transcriptomes. The 118 full-length genes were divided into 8 clans and 29 families. The CYP71 clan included all A-type genes (52) belonging to 11 families. The other seven clans possessed 18 families containing 66 non-A-type genes. Two new gymnosperm-specific families were discovered, and were named CYP864 and CYP947 respectively. Protein sequence alignments revealed that all of the T. chinensis CYP450s hold distinct conserved domains. The expression patterns of all 118 CYP450 genes during the long-time subculture and MeJA elicitation were analyzed. Additionally, the expression levels of 15 novel CYP725 genes in different Taxus species were explored. Considering all the evidence, 6 CYP725s were identified to be candidates for Taxol biosynthesis. The cis-regulatory elements involved in the transcriptional regulation were also identified in the promoter regions of CYP725s. This study presents a comprehensive overview of the CYP450 gene family in T. chinensis and can provide important insights into the functional gene studies of Taxol biosynthesis.
Highlights
Taxol, the main bioactive component of the Taxus species, is a highly effective anti-cancer agent widely used in the treatment of various sarcomas, melanomas, and carcinomas (Murphy et al, 1993)
A total of 118 full-length and 175 partial Cytochrome P450s (CYP450s) genes were identified in T. chinensis
Establishing a systematic nomenclature for these CYP450s; (3) mining the candidate CYP450s that are likely related to Taxol biosynthesis; and (4) analyzing the cis-regulatory elements in the promoters of CYP725 genes to provides useful information to the transcriptional regulation of Taxol biosynthesis
Summary
Taxol (generic name paclitaxel), the main bioactive component of the Taxus species, is a highly effective anti-cancer agent widely used in the treatment of various sarcomas, melanomas, and carcinomas (Murphy et al, 1993). Understanding the biosynthetic pathway of Taxol and the enzymes that catalyze this series of reactions and their underlying molecular mechanism is essential. The Taxol biosynthetic pathway starts with the cyclization of the universal diterpenoid precursor geranylgeranyl diphosphate to taxa-4(5),11(12)-diene. This taxane core is decorated with a series of eight Cytochrome P450 (CYP450)-mediated oxidations, three CoA-dependent acylations, and several other transformations that lead to baccatin III, to which the C13side chain is appended to afford Taxol (Jennewein et al, 2001; Croteau et al, 2006). The CYP450 genes responsible for C1 hydroxylation, oxetane formation, C9 oxidation of the taxane core, and C2′-sidechain hydroxylation in Taxus remain unidentified
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