家蚕bHLH基因的染色体定位与系统发生分析

Chromosomal Localization and Phylogenetic Analysis of bHLH Genes in the Silkworm,Bombyx mori

bHLH转录因子在真核生物生长发育调控中具有重要作用。以原有家蚕bHLH基序为查询序列,从最新版本的家蚕基因组数据库(SilkDB)中鉴定出52个家蚕bHLH家族成员,并将其中47个成员的编码区域定位到家蚕染色体上。分析家蚕与黑腹果蝇、蜜蜂、赤拟谷盗bHLH基序氨基酸序列的系统发生,结果呈现如下特点:(1)4种昆虫ASCa家族中的Ase蛋白功能相近,家蚕中有2种果蝇Ac蛋白的同源蛋白,而没有果蝇Sc和Lsc的同源蛋白;(2)4种昆虫HES家族中的Hairy蛋白功能相近,家蚕BmHES3可能是果蝇Dpn或Side的同源蛋白,家蚕BmHES1和BmHES2分别是赤拟谷盗HES1和蜜蜂HES2的同源蛋白;(3)家蚕比其它3种昆虫分别多出1个Clock家族与AHR家族成员,意味着家蚕在长期的人工驯化过程中可能在昼夜节律的调控与对外源毒素刺激的响应方面演化出了新的机理。汇总了与家蚕52个bHLH成员对应的果蝇、蜜蜂和赤拟谷盗同源蛋白序列及44种家蚕bHLH蛋白序列登录号。以上结果可为进一步开展家蚕bHLH基因结构与功能研究提供较为系统、完整的背景资料。

bHLH transcription factors play important roles in the regulation of eukaryotic growth and development.In present study,52 bHLH family members were identified from the latest version of silkworm （Bombyx mori） genome database （SilkDB） by using the previously reported bHLH motifs as query sequences.Coding regions for 47 members have been mapped on B.mori chromosomes.Phylogenetic analyses to amino acid sequences of bHLH motifs from B.mori,Drosophila melanogaster,Apis mellifera and Tribolium castaneum revealed the following characteristics：（1）functions of Ase protein of the ASCa family in these 4 insect species were similar.B.mori has 2 proteins homologous to Ac protein of D.melanogaster but does not have homologs with Sc and L＇sc proteins of D.melanogaster.（2）Functions of Hairy protein of the HES family in these 4 insect species were similar.Silkworm BmHES3 is a homologous protein of either Dpn or Side of D.melanogaster.Silkworm BmHES1 and BmHES2 are homologous proteins of T.castaneum HES1 and A.mellifera HES2 respectively.（3） B.mori has one more member in Clock and AHR families over the other three insect species respectively,suggesting that B.mori might have evolved new mechanisms to cope with different circadian rhythms and respond to stimulation of various exogenous toxins it confronted during long period domestication.This article also listed accession numbers of D.melanogaster,A.mellifera and T.castaneum homologous proteins to all the 52 B.mori bHLH members and those of 44 B.mori bHLH proteins.The above results provide systematic and complete background information for further studies on structures and functions of B.mori bHLH genes.