控制水稻光合产物运输SEM1基因的克隆与功能解析

光合作用是指绿色植物吸收光能，把CO2和水合成碳水化合物的过程。蔗糖是高等植物中光合作用的主要产物，是碳水化合物贮藏和累积的主要形式，也是光合同化产物从"源”到“库”的主要载体。水稻源器官制造的光合同化物以蔗糖形式经韧皮部运输到籽粒，是水稻产量形成的基础，这个过程包括蔗糖在源叶器官中的装载、长距离运输和在库器官中的卸载三个阶段。目前，对于两头阶段即装载和卸载取得较好的进展，而对最复杂的中间阶段，即长距离运输了解还很有限，缺少比较系统的研究。前期，我们筛选水稻突变体库，获得了一份叶片过量积累蔗糖的突变体sem1-1，细胞学和电镜试验表明，水稻叶片和茎秆的维管束韧皮部通透性异常是造成蔗糖不能正常运输的主要成因，图位克隆了该基因，编码一个功能未知的蛋白。本项目拟在此基础上，通过细胞学、遗传学、生理生化和分子生物学实验进一步解析该基因在光合产物在运输中作用机制，为培育高光效的水稻材料提供理论支撑。

Photosynthesis is the process that green plants absorb light energy and synthesize CO2 and water into carbohydrates. Sucrose is the main form of carbohydrate storage and accumulation in higher plants, and also the main carrier of photosynthate from source to sink. The photosynthate produced by the source organ in rice is transported to the grain through the phloem in the form of sucrose, which is the basis of rice yield formation. This process includes three stages: sucrose loading in the source leaf organ, long-distance transportation and unloading in the sink organ. At present, good progress has been made in both loading and unloading stages, while the most complex intermediate stage, namely long-distance transportation, is still very limited. Previously, we screened rice mutant library and obtained a mutant sem1-1 with excessive accumulation of sucrose in leaves. Cytological and electron microscopic experiments showed that abnormal phloem permeability in vascular bundles of rice leaves and stems was the main cause of abnormal sucrose transport. The gene was cloned by map-based cloning method and encoded a protein with unknown function. On this basis, the project intends to further elucidate the mechanism of the SEM1 gene in photosynthate transport, providing a theory for the cultivating rice materials with high photosynthetic efficiency.