麻疯树佛波酯合成代谢网络与关键调控基因的功能分析

Jatropha curcas L. has received much attention as a feedstock for biodiesel production. In addition to being a valuable source of oil, the seed kernels are also rich in protein. The protein rich seed meal of J.curcas is not used as animal feed due to the presence of phorbol esters, a diterpene. The majority (70-75%) of phorbol esters present in the seed is extracted with the oil fraction, others in the seed meal. Consequently, the presence of phorbol esters not only disturb the biodiesel process, production and exploiting, but also block the the seed meal employed as the animal feed. This project will firstly apply the transcriptome sequencing technology to compare gene expression profiles of developing toxic and non-toxic J.curcas seeds at various stages, and globally find out the metabolic biosynthesis of phorbol esters. Then clone and functional characterize the seed specific key genes involved in the biosynthesis of phorbol esters. Also we will isolate and functional characterize the phorbol esters biosynthesis related diterpene synthases, based on the genome sequences. This project will lay a solid foundation for the plant breeding to generate low in or free of phorbol esters varieties using transgenic technology.

麻疯树是备受国际社会的关注生产生物柴油的原料。其种仁含有高油脂含量且富含蛋白质，但因为毒性二萜物质佛波酯的存在而无法作为动物饲料的原料。麻疯树种子中的佛波醇酯有70%-75%存在于油脂中，而其余的存在于饼粕中。佛波酯毒性物质一方面妨碍对生物柴油的加工、生产、利用，同时饼粕因为其毒性不能做为饲料直接利用。本项目拟通过对有毒（高佛波酯含量）麻疯树不同发育期种子的转录组分析和通过比较无毒麻疯树（低佛波酯含量）不同发育期种子的转录组数据分析，系统了解麻疯树种子中佛波酯的合成代谢途径；根据基因组数据,克隆在种子中特异表达和影响佛波酯合成代谢中的关键基因（二萜合酶基因和环化二萜（巴豆烷）骨架进行修饰相关基因等）并分析基因的催化活性和特性和阐明关键基因的功能,为通过转基因技术培育低含量佛波酯的改良品种奠定基础。

麻疯树种仁虽然具有高油脂含量且富含蛋白质，但同样含有毒性二萜物质佛波酯。麻疯树种子中的佛波酯有70%-75%存在于油脂中，而其余的存在于饼粕中。佛波酯毒性物质一方面妨碍生物柴油的加工、生产、利用，同时饼粕因为其毒性不能做为动物饲料直接利用。本项目首先进行了有毒（高佛波酯含量）麻疯树和无毒麻疯树（低佛波酯含量）早期（25 DAP）和晚期（41 DAP）发育点种子的表达谱测序，筛选同发育期有毒麻疯树和无毒麻疯树种子的差异表达基因发现： 25 DAP存在36个差异表达基因，41 DAP有283个差异表达基因，且有9个基因在两个发育点均呈一致响应；差异表达基因中有多个酰基转移酶类或羟基化酶类基因；25个CYP450基因呈现差异表达；确定了5个相关基因且进行了麻疯树遗传转化。另外，从麻疯树中分离出59个TPS基因，其中26个属于TPSa亚家族。8个在种子中有表达的TPSa基因进行功能分析，结果表明JcTPS09和JcTPS11参与了佛波酯骨架结构蓖麻烯的合成。这些研究结果将为通过转基因技术培育低含量佛波酯的改良品种奠定基础。