SWEET (Sugars Will Eventually be Exported Transporters) 基因编码糖转运蛋白，负责糖跨膜运输。玉米SWEET1b基因是定位在气孔副卫细胞膜上的葡萄糖转运蛋白，在灌浆期通过碳饥饿反馈调节气孔开放，调控光合速率。但SWEET基因是否在营养生长期参与光合作用的反馈调节还不清楚。SWEET1a与SWEET1b基因同在CladeⅠ分支上，突变SWEET1a基因导致玉米发育早期叶片失绿，但基因功能未知。在本项目中，将对SWEET1a基因的表达模式、表达部位及转运底物进行分析，并通过组学研究SWEET1a基因与SWEET1b基因在营养生长和生殖生长转换期表达调控机制及协同作用关系，解析SWEET1类基因在光合作用中的功能。通过本项目的实施，可以阐明玉米SWEET基因对光合作用反馈调节机制，探索在玉米“源-库-流”三要素中通过“增源”来提高玉米产量。

Sugar transporters encoded by SWEET (Sugars Will Eventually be Exported) genes are responsible for sugar trans-membrane transport. Maize SWEET1b gene is a glucose transporter localized on the membrane of subsidiary cells, which regulated positively stomatal opening and photosynthetic rate through carbon starvation feedback during the grain-filling stage. However, it is not clear whether SWEET gene is involved in the feedback regulation of photosynthesis during the vegetative growth period. Both SWEET1a and SWEET1b gene belonged to CladeⅠ, and sweet1a mutant showed leaf chlorosis at vegetative growth stage, but SWEET1a gene function is unknown. In this project, we focus on analyzing SWEET1a gene’s expression mode, localization and transporting substrate, and studying transcriptional regulation mechanism and synergistic effect relationship of SWEET1a gene and SWEET1b gene in the vegetative growth and reproductive growth transition period with transcriptome and metabolome, so as to understand the function of SWEET1 gene in photosynthesis. The goal of this project is to clarify the feedback regulation mechanism of maize SWEET gene on photosynthesis and explore improving grain yield by "increasing source" among the three elements of "source-sink-flow".