家蚕组织蛋白酶基因家族的鉴定及表达特征分析

Identification and expression pattern of cathepsin family in silkworm (Bombyx mori)

摘要:

家蚕是鳞翅目完全变态昆虫，在其变态过程中伴随着巨大的形态变化，包括旧组织的解离和新组织的形成，在这过程中有多种组织蛋白酶参与。组织蛋白酶是一类细胞内蛋白酶，广泛存在于各个物种中，包括组织蛋白酶B、H、L等几个亚家族。对家蚕组织蛋白酶的研究将有利于阐明家蚕变态发育的详细过程。通过对家蚕基因组数据库进行筛选，共在家蚕中鉴定到13种组织蛋白酶，并对这13种组织蛋白酶的基本信息和表达模式进行了分析。另外，利用家蚕基因芯片数据和荧光定量PCR分析，鉴定编号为BGIBMGA004622的基因为卵巢特异表达的组织蛋白酶L亚家族基因。该基因全长1 209 bp，编码402个氨基酸。经过序列分析，该酶与其他物种的组织蛋白酶L具有较高的同源性，其活性位点高度保守，且与鳞翅目的组织蛋白酶L在进化上聚为一支。同时，对该基因进行克隆并原核表达，结果显示重组蛋白以包涵体的形式表达。定量PCR结果显示，该酶在蛹发育初期表达量逐渐升高，至蛹3 d达到最高值，推测其可能参与卵巢与卵母细胞的发育过程。

Abstract:

Silkworm is a holometabolous insect of Lepidoptera. During metamorphosis, significant morphological changes happen including the dissociation of old tissues and remodeling of new tissues. It has been reported that cathepsins are involved in these processes. Cathepsin is a kind of intracellular proteinase that exists in many species. It includes some subfamilies like cathepsin B, H and L. The studies on cathepsin are useful for clarifying the details of silkworm metamorphosis process. In total, 13 cathepsins were identified by screening the silkworm genome database. The basic information and the expression patterns about these genes were analyzed. Interestingly, an ovary-specific cathepsin L gene (Gene ID: BGIBMGA004622) was investigated by the data of silkworm microarray and real-time quantitative PCR (qPCR). The full-length cDNA is 1 209 bp, encoding a protein with 402 amino acids. Sequences alignment revealed that it has a high sequence similarity with cathepsin L of other species, and it is highly conserved in the active-site of the enzyme. The phylogenetic analysis showed that ovary-specific cathepsin L is clustered with other lepidopterous insects. Furthermore, this gene was cloned and prokaryotic expressed. Recombinant protein was present in inclusion body. Importantly, the qPCR result showed that the expression level of this gene is increasing during the early stage of pupal development and reaches the highest value at the 3rd day of pupal stage, which suggests that this gene may be involved in the process of development of the ovary and oocyte.