储藏根是薯类特有的能量储存器官，其发育及碳流分配决定特定代谢物的大量富集，解析该生物学过程的调控机制是改良薯类作物的产量和品质的基础。木薯储藏根大量富集淀粉，因此淀粉合成是其主导的代谢过程。本项目以可溶性淀粉合成酶II (SSII) 为主要目标基因，基于SSII-RNAi转基因木薯储藏根脂肪酸大幅度提高和淀粉含量降低的表型，研究SSII在淀粉合成酶复合体中的核心作用及通过与其它蛋白互作调控储藏根碳流分配的机制。以野生型和下调淀粉合成酶表达的转基因木薯为研究材料，利用GPC分离造粉体蛋白，通过Co-IP、BiFC、Pull-down、酵母双杂交等技术分析SSII参与淀粉合成酶复合体的组装模式及与AGPase、GBSS和PPDK激酶等互作的调控；结合储藏根淀粉和脂肪酸分析及基因表达的变化，解析SSII在调控储藏根碳流分配中的分子模式和抗性淀粉形成的方式，为薯类品质改良提供理论指导和技术支持。

The development and carbohydrate partitioning of storage root, the energy storage organ of root and tuber crops, determine the accumulation of specific metabolites. Revealing the regulatory mechanism of the biological processes can provide the fundamental technology for yield and quality improvement in root and tuber crops. Cassava storage roots accumulate large amount of starch, thereby, starch biosynthesis is the leading metabolism. The project focuses on the soluble starch synthase II (SSII) and studies its function in the complex of starch biosynthetic enzymes and carbohydrate partitioning through protein-protein interaction with others, which is based on the phenotypic changes of dramatically increased lipid content and reduced starch amount in the storage roots of SSII-RNAi transgenic cassava plants. Using the wild type and transgenic cassava plants that are down-regulated expression of starch synthases, the interplay of SSII in the organizing the complex of starch synthetic enzymes and the interaction with AGPase, GBSS and PPDK were studied using various techniques such as Co-IP, BiFC and Pull-down. In combination with starch and lipid analysis and gene expression changes, the molecular mode of SSII for regulating carbohydrate partitioning in storage roots and formation of resistant starch will be revealed. The study will provide the fundamental knowledge and technology for quality improvement of root and tuber crops.