[Construction of yeast cell factories for production of azadirachtin precursor tirucalla-7,24-dien-3β-ol].

Azadirachtin, as a botanical insecticide, is a highly oxidized limonoid triterpenoid existing in the seeds of Azadirachta indica. However, due to the low content in the seeds, the production of azadirachtin by seed extraction has low yield. Chemical synthesis of azadirachtin is characterized by complex process and low yield. Synthetic biology provides an alternative for the supply of azadirach-tin. In this study, two oxidosqualene cyclases AiOSC1 and MaOSC1 respectively derived from A. indica and Melia azedarach were identified in yeast. A yeast strain producing tirucalla-7,24-dien-3β-ol was constructed by integration of AiOSC1, Arabidopsis thaliana-derived squalene synthase gene(AtAQS2), and Saccharomyces cerevisiae-derived truncated 3-hydroxy-3-methyl-glutaryl coenzyme A reductase gene(PgtHMGR) into the delta site of yeast. Then, the function of MaCYP71BQ5 was successfully verified in yeast after this gene was introduced into the constructed yeast strain. This study not only laid a foundation for the biosynthesis of tirucalla-7,24-dien-3β-ol, but also provided a chassis cell for the functional identification of cytochrome oxidases(CYP450 s) in azadirachtin biosynthesis pathway.