家蚕GH18家族几丁质酶的系统进化和BmChi的时期表达分析

Phylogenetic Analysis of GH18 Family Chitinases and Temporal Expressional Profile of BmChi in the Silkworm,Bombyx mori

昆虫GH18家族几丁质酶主要参与昆虫蜕皮、细胞增殖和免疫等生理过程。为了系统开展家蚕GH18家族基因的研究,通过多物种几丁质酶的系统进化分析鉴定了8个家蚕GH18家族成员,并根据含有糖苷水解酶18(Glyco_18)催化结构域和几丁质结合结构域的不同将其分为6类,其中,各物种的CHT5具有典型几丁质酶结构。家蚕GH18家族成员中,BmChiR-1具有5个Glyco_18催化结构域和6个几丁质结合结构域,其它7个成员均只有1个Glyco_18催化结构域,BmCHT12还有1个ChitnaseA_N端结构域。8个家蚕GH18家族成员的基因分布在7条染色体上。通过半定量RT-PCR调查家蚕CHT5基因Bm-Chi在家蚕各发育时期的转录表达模式,该基因在蜕皮、化蛹、羽化等发育时期均有高水平表达,推测BmChi在蚕体旧表皮几丁质的降解过程中发挥重要作用。

Insect GH18 family chitinases are mainly involved in the physiological processes of molting, cell proliferation and immunization. In order to systematically investigate silkworm GH18 family genes, we identified 8 members of GH18 family, which can be classified into 6 classes based on their differences in glycoside hydrolase 18 （Glyco_18） catalytic domain and chitin binding domain, in silkworm via phylogenetic analysis of chitinase from multi-species. Among them, CHT5 of various species had typical chitinase structure. In silkworm GH18 family members, BmChiR-1 contains 5 Gly- co_18 catalytic domains and 6 chitin binding domains, while each of the other 7 members only contains 1 Glyco_18 catalytic domain, and BmCHT12 contains 1 additional ChitinaseA_N terminal domain. The 8 silkworm GH18 family members was found to locate on 7 chromosomes. The transcriptional profile of silkworm CHT5 gene BmChi was ana- lyzed by semi-quantitative RT-PCR, and the results indicated that BmChi had remarkably high expressional level during molting, pupation and eclosion, suggesting that BmChi plays an important role in the degradation of chitin in original cuticle of silkworm.