中国柿果实扩展蛋白基因的cDNA克隆与序列分析

以中国柿膨大期和成熟衰老期果实cDNA为模板。参照其它植物细胞壁扩展蛋白（expansin）基因序列设计兼并引物。进行RT-PCR。得到的扩增产物与pUCm—T质粒连接。转化大肠杆菌JMl09。任意挑选阳性克隆。进行序列测定。得到2个序列不同的expansin cDNA片段。分别命名为Cdk—Exp1和Cdk—Exp2。2个片段均存在expansin基因的保守区域。即8个半胱氨酸残基和3个色氨酸残基。Cdk—Expl和Cdk—Exp2分别由531个碱基和522个碱基组成。编码177个和174个氨基酸，二者核苷酸与氨基酸序列同源性分别高达92．635％和92．156％。中国柿果实expansin cDNA与草莓、番茄和桃果实的扩展蛋白基因在氨基酸水平上有较高的同源性。

Cloning and Sequencing of Expansin cDNA in the Fruits of Chinese Persimmon

With the cDNA in the fruits at the enlarging and maturing stages as the templates and according to the gene sequences of the expansins in other plants,the degenerate primers were constructed to conduct RT-PCR.The product of the amplification were combined with plasimd pUCm-T and then transformed into E.coli JM109.The positive clones were randomly chosen and sequenced,and then two fragments of the expansin cDNA with different sequences were obtained;the fragments were named Cdk-Exp1 and 2.Both the two fragments were located in the conservative regions of expansin gene,i.e.8 cysteine residuals and three tryptophan residuals.Cdk-Exp1 and 2 consisted of 531 bases encoding 177 amino acids and 522 bases encoding 174 amino acids,respectively;the homology of their amino acid sequences reached 92.635% and 92.156% respectively.The expansin cDNA in the fruits of Chinese persimmon was highly homogenous to those in the fruits of strawberry,tomato,and peach on amino acid level.