水稻分支酶基因 Sbe1和 Sbe3 cDNA的克隆及全序列分析

 通过改良的RT PCR法合成了水稻未成熟种子胚乳cDNA库，并以此为模板，用PCR技术从粳稻品种武运粳7号中克隆了分别编码淀粉分支酶SBEⅠ和SBEⅢ的2个基因Sbe1和Sbe3。序列分析表明，克隆Sbe1和Sbe3基因的大小分别为2490 bp和2481 bp，包含了基因完整的编码序列。Sbe3基因与已发表基因全序列完全相同，同源性达100%；Sbe1基因与已发表基因序列有4个碱基不同，同源性为99.84%，推导氨基酸序列的差异为2个。

cDNA Cloning and Sequence Analysis of Rice Sbe1 and Sbe3 Genes

The starch branching enzyme (SBE) is a key enzyme in amylopectin biosynthesis and there are two major isoforms in rice, named SBEⅠ and SBEⅢ, which are encoded by the Sbe1 and Sbe3 genes, respectively. These two genes were cloned from the template cDNA library, which was synthesized by improved RT PCR technique from the mRNAs of the immature rice seeds of japonica rice Wuyunjing 7. DNA sequencing analysis showed that the size of the cloned Sbe1 and Sbe3 cDNAs were 2490 bp and 2481 bp, respectively, and carried their entire coding sequences. Comparison analysis indicated that the Sbe3 sequence was the same as the reported and their homology was 100%. There were only four base pairs difference, which resulted in two deduced amino acids alteration, between the cloned Sbe1 cDNA and the reported.