家蚕神经肽基因的筛查及成熟肽的预测

Neuropeptide gene screening and mature peptide prediction in the silkworm,Bombyx mori

神经肽(neuropeptide)是家蚕Bombyx mori体内重要的调控物质。为了充分理解神经肽对家蚕发育的调控,扩充家蚕神经肽的数量,本研究利用BLAST的tblastn程序结合OpenOffice软件的查找程序,基于其他昆虫和无脊椎动物神经肽的同源性和保守的结构特点,在家蚕基因、理论蛋白质数据库及NCBI中进行全面而系统的基因筛查;并利用各种在线工具对所筛查到基因和理论蛋白质的结构和成熟肽进行预测分析。结果共获得allatostatin-A(AST-A),allatostatin-B(AST-B),allatostatin-C(AST-C),allatropin(AT),ecdysis-triggering hormone(ETH),crustaceancardioactive peptide(CCAP)和FMRFamide等31个神经肽基因家族,包括37个神经肽基因亚家族,共计44个神经肽基因;预测出193个成熟的神经肽,其中73个根据家族同源性预测在C末端发生酰胺化,而6个被预测在N末端发生了环化,9个被预测酪氨酸发生了硫酸化。大部分成熟神经肽都具有明显的家族结构特征,但proctolin,CCAP及CAPA-PK成熟肽结构上与其他昆虫相比有所扩展。结果提示,家蚕神经和内分泌细胞产生了几乎在所有昆虫中具有的神经肽前体;进化过程中大部分成熟神经肽的氨基酸序列在种间产生了差异,但家族特征性基序高度保守。本研究为神经肽功能研究以及神经肽对家蚕发育尤其是蛹期发育调控的研究奠定了基础。

Neuropeptides play an important role of regulation for the silkworm,Bombyx mori. To fully comprehend the regulation of neuropeptides in the growth of B. mori and to get more neuropeptides in B. mori,the online program tblastn of BLAST and the search program of OpenOffice software were used to screen genes encoding putative neuropeptide precursors in the databases of silkworm genome and theoretical proteins based on the homology and the structure of the neuropeptides conserved in other insects and invertebrates. Several online programs were used to analyze the structures of the genes and the theoretical proteins to predict the mature peptides. As results,31 neuropeptide gene families with 37 gene subfamilies including allatostatin-A （AST-A）,allatostatin-B （AST-B）,allatostatin-C （AST-C）,allatropin （AT）,bombyxin,ecdysis-triggering hormone （ETH）,crustacean cardioactive peptide （CCAP）,and FMRFamide were identified. A total of 44 neuropeptide genes and 193 mature peptides were predicted. Among them,73 neuropeptides are amidated at the C-terminal,six neuropeptides are cyclized at the N-terminal,and nine neuropeptides are sulfated. Most of the mature peptides share the similarity because they belong to the same family. But compared with that of other insects,mature peptides of proctolin,CCAP and CAPA-PK are more advanced in the structure. The results suggest that the neuropeptide precursors,which are possessed by almost all the insects,are produced by nerve and endocrine cells of B. mori,and in the course of evolution,differences in the amino acid sequences for most mature peptides formed among different insect species,but the motifs for the same family are highly conserved. This study provided useful information for future research on functions of neuropeptides,which will give us novel insights into the regulation of developmental process,especially at the pupal stage,in the silkworm.