梨果实中肉桂醇脱氢酶基因的克隆与序列分析

肉桂醇脱氢酶（CAD）是木质素生物合成过程中的一个关键酶。本研究分别提取了＂砀山酥梨＂及＂幸水＂梨果肉总RNA,并通过RT-PCR、克隆和测序,成功获得了2个CAD的大小为689bp的cDNA片段,并分别命名为PB-CAD（登录号：FJ478151）和PP-CAD（登录号：FJ478152）。在核苷酸水平上,这两个基因片段只有4个碱基的差异,编码相似性达99.6%的两个氨基酸序列,该序列由229个残基组成。通过蛋白质序列比较,发现梨果实CAD与许多植物中CAD氨基酸序列极为相似,与苹果Malus domestica（AAC06319）、梅Prunus mume（BAE48658）、枇杷Eriobotryajaponica（ABV44810）和葡萄Vitis vinifera（CAO21890）的相似性分别达到97.8%、95%、92.6%和83.4%。 Cinnamyl alcohol dehydrogenase （CAD） plays a key role in lignin biosynthesis. Two cD- NA fragments, designated as PB-CAD （ GenBank accession No. FJ478151） and PP-CAD （ Gen- Bank accession No. FJ478152）, coding for CAD were cloned using RT-PCR from ＇Dangshansuli＇ and ＇Kousui＇ pear cultivars and sequenced, respectively. Both cDNAs were 689 bp in length, and differed by only 4 bp in nucleotide sequences. Theoretically, they would encode two peptides of 229 amino-acid residues that shared 99. 6% of identity with each other. Sequence alignment showed that the two deduced amino acid sequences were 97. 8% identical to CAD from Malus domestica （AAC06319）, 95%to CAD from Prunusmume （BAE48658）, 92. 6% to CAD from Eriobotryaja- ponica （ABV44810）and 83.4% to CAD from Vitis vinifera （CAO21890）, respectively.