水稻糖苷水解酶基因OsBE1在叶绿体发育中的功能

叶绿体在植物碳水化合物代谢中起着至关重要的作用，然而有关碳水化合物代谢在叶绿体发育过程中的功能却知之甚少。从水稻中克隆了一个Oryza sativa Branching Enzyme 1 (OsBE1)基因，该基因编码一个糖苷水解酶13家族的蛋白。OsBE1与拟南芥AtBE1的一致性为66%，但与水稻典型淀粉分支酶的一致性仅约为40%。该基因的T-DNA插入功能缺失突变体osbe1幼苗白化，且其白化表型不能用外源糖类拯救。osbe1突变体幼苗最终在三叶期死亡。淀粉染色表明，osbe1突变体中淀粉的含量与野生型无明显差异。进一步的研究表明，osbe1突变体叶绿体数目较少，且无明显的基质片层结构。构建了OsBE1基因过量表达载体pCAMBIA1300-35S-OsBE1，并将其转化水稻中花11。获得的108株转基因水稻中，77株表现不同程度的黄化。本文初步揭示了碳水化合物代谢调控叶绿体发育的机制，并为深入研究糖苷水解酶BE1的功能奠定了基础。

Functional Characterization of the Glycoside Hydrolase Encoding Gene OsBE1 during Chloroplast Development in Oryza sativa

Chloroplast plays an important role in plant carbohydrate metabolism; however the function of carbohydrate metabolism in the chloroplast development is poorly understood. The Oryza sativa Branching Enzyme 1 (OsBE1) gene, encoding a glycoside hydrolase family 13 protein, was cloned from rice. The identity between OsBE1 and Arabidopsis AtBE1 is 66%, but only 40% between OsBE1 and the classical starch branching enzymes in rice. A T-DNA insertion mutant of OsBE1 gene was identified. The seedlings of the osbe1 mutant were albino, and died at the three-leaf stage. This albino phenotype could not be rescued by exogenous carbohydrate. Starch staining showed no obvious difference in starch content between osbe1 and the wild type. Further studies showed that there were less chloroplasts in osbe1 mutant than in wild type, and there was no obvious stroma lamella in the osbe1 chloroplast. The overexpression vector pCAMBIA1300-35S-OsBE1 was constructed and transformed into rice variety Zhonghua 11. Finally, 108 transgenic lines were obtained and 77 lines of them showed etiolation in different degrees. The work not only sheds a novel insight into the regulation mechanism of carbohydrate metabolism on chloroplast development, but also lays a foundation for further understanding of the OsBE1’s function.