罗汉果是重要传统中药和甜料植物，适栽区域狭窄，其主要活性成分和甜味成分甜苷V在鲜果中仅含3～4‰，低含量造成甜苷V生产成本居高不下。栽培和育种技术研究周期长、难度大，本课题通过甜苷V合成关键酶基因功能的验证和调控研究，试图从分子水平探索提高甜苷V含量的新途径。拟在前期研究基础上对罗汉果甜苷V合成关键酶CS基因和侧枝甾醇合成关键酶CAS基因功能进行验证，筛选能使CS基因高表达的强启动子和增强子，以增加前体物质罗汉果醇，同时RNA干扰抑制旁路CAS基因的表达减少甾醇类化合物的合成，从而明显提高甜苷V含量。本研究成果不仅在一定程度上阐明了甜苷V生物合成的机理，也为罗汉果转基因育种提供理论依据，并提供遗传工程的靶基因。

Siraitia grosvenorii,an importantly traditional Chinese medicine and sweetner plant,has a narrowly suitable area.The major bioactive component and sweet gradient is mogroside V which only accounts to 3-4‰,and its low content results in that the production cost of mogroside V remains high.The cycle of cutivation and cross-breeding is very long and difficult.In this study we attempt to explore new ways to improve the content of mogroside V by verifying and regulating gene functions of key enzymes involved in its biosyhtesis on basis of preliminary study,and find strong promoter and enhancer for CS in order to increase the content of mogrol,simutaneously we try to suppress the expression of the branch gene CAS by RNA interference to reduce biosynthesis of sterol,which causes the improvement of mogroside V finally.This study will not only demonstrate the biosynthetic mechanism for mogroside V to some extent,but also will provide a theoretical basis and target gene for Siraitia grosvenorii in transgenic breeding and genetic engineering.

罗汉果是重要传统中药和甜料，植物适栽区域狭窄，其主要活性成分和甜味成分甜苷V在鲜果中仅含3～4‰，低含量造成甜苷V生产成本居高不下。栽培和育种技术研究周期长、难度大，本课题建立并筛选了罗汉果的最佳遗传体系，通过甜苷V合成关键酶基因功能的验证和调控研究，从分子水平探索了提高甜苷V含量的新途径。课题对罗汉果甜苷V合成关键酶CS基因和侧支甾醇合成关键酶CAS基因功能进行验证，克隆并验证了CS和CAS基因的启动子序列，以期从分子水平增加罗汉果甜苷V的前体物质，从而明显提高甜苷V含量。本研究成果不仅在一定程度上阐明了甜苷V生物合成的机理，也为罗汉果转基因育种提供理论依据，并提供了遗传工程的靶基因。