西瓜果实光合产物卸载与糖分积累进化的分子调控机制

光合产物从“源”运输卸载并积累到“库”，是作物增加产量和提高品质的物质基础。有关棉子糖等寡糖如何在果实韧皮部筛管/伴胞水解？如何进一步卸载蔗糖、糖分进入果肉细胞及在液泡储存？这关键四步的分子机制尚不十分清楚。本课题组已初步确定控制西瓜这四个关键环节的基因分别为ClAGA1、ClVST1、ClSWEET3和ClTST2，并通过CRISPR/Cas9技术获得四个关键基因敲除且有预期表型的T2后代。在此基础上，本项目拟通过常规有性杂交获得双敲、三敲和四敲除ClAGA1、ClVST1、ClSWEET3和ClTST2的后代，系统性解析四个关键节点基因在控制西瓜光合产物卸载与糖含量中的单独和累积效应。利用酵母单杂交、EMSA和Luc荧光蛋白等技术揭示调控四个关键基因的转录因子；明确其受激素调控的分子机制；解析四个关键基因及其调控基因的结构变异及进化驯化机制，为西瓜品质育种和高品质栽培提供技术指导。

The transportation and accumulation for photosynthesis from "source" to “sink” tissues are the basis for increasing crop yield and improving quality. The molecular mechanism to hydrolyze RFOs (Raffinose Family Oligosaccharides), unload and transport sugars in the fruit sieve element/companion cell and storage in the vacuole, is still unclear. Our research has preliminarily determined that the genes in the four key stages of watermelon are involved with ClAGA1, ClVST1, ClSWEET3, and ClTST2. The expected phenotype was observed of the T2 CRISPR/Cas9 mutation lines of ClAGA1, ClVST1, ClSWEET3, and ClTST2. On this basis, this project intends to double, triple and tetra mutation of ClAGA1, ClVST1, ClSWEET3, and ClTST2 to answer single and dosage effect in the control of the sugar content of watermelon fruits. We will reveal the transcription factors for regulating four key genes by using yeast single hybridization, EMSA and Luc fluorescent protein. We will investigate the mechanism for hormone signal to activate these four genes and related transcription factors. The structural variation, evolution and domestication mechanism of four key genes and their regulatory genes will be analyzed. It will provide technical guidance for watermelon high-quality breeding and cultivation.