家蚕组织蛋白酶D基因的克隆、序列分析及其表达谱研究

组织蛋白酶D (cathepsin D，CtD)是溶酶体内天冬氨酸内切蛋白酶，参与机体多种生理病理过程，尤其在昆虫的发育变态过程中起着重要作用。利用NCBI上登录的组织蛋白酶D基因核酸序列和家蚕Bombyx mori表达序列标签（expressed sequence tags, EST）数据库，进行电子克隆获得家蚕组织蛋白酶D (BmCtD) 基因的全长cDNA (DQ010007)。该cDNA大小为1 543 bp,其中ORF长1 152 bp,同源性分析表明BmCtD与其他物种的CtD具有较高的相似性。BmCtD的mRNA存在选择性拼接，另外一种mRNA形式命名为BmCtDⅠ。RT-PCR实验表明该基因在本实验所调查的家蚕不同发育时期和组织中都有表达。

Sequence analysis and expression of cathepsin D in the silkworm, Bombyx mori

Cathepsin D is lysosomal endoproteolytic enzyme which is thought to play key roles in the developmental and physiological process in organisms. The nucleic acid sequence of reported silkworm cathepdin D was used to tBLASTn search against the silkworm EST database. The ESTs with high score were clustered and assembled into a consensus sequence. Based on the consensus sequence, the aspartic proteases of Bombyx mori was cloned and identified, termed as BmCtD (GenBank accession number: DQ010007). The cDNA was 1 543 bp at length with an open reading frame of 1 152 bp, and there were alternative splices in BmCtD. The deduced amino acid sequence of the BmCtD shared high similarity with that of cathepsin D in other species. The results of RT-PCR showed that the gene was expressed at all examined developmental stages and tissues of B. mori.