家蚕过剩半月纹退化腹肢突变基因(E^(dl))的分子定位

Molecular Mapping of Extra-crescents and Degenerated Abdominal Legs Mutational Gene(E^(dl)) in Silkworm,Bombyx mori

家蚕E群基因是第6染色体上的一群拟复等位基因,其突变表型包括幼虫斑纹过剩或减少、附肢变异、环节畸形、器官异常以及胚胎期致死等,对家蚕E群突变体突变基因的分子定位研究,有助于深入探究鳞翅目昆虫躯体模式建立的分子调控机制。过剩半月纹退化腹肢突变(Edl)是家蚕E群突变中发现的唯一一个隐性突变,其形态特征为:幼虫第1对腹足退化,残留基部,第3腹节背面有过剩半月纹。利用家蚕雌完全连锁的特点,采用正常型品系大造与Edl突变体配制连锁分析群体BC1F[(大造×Edl)♀×Edl♂],同时配制基因定位群体BC1M[Edl♀×(大造×Edl)♂]。首先在家蚕同源异型(homeotic,Hox)基因族及其附近区域筛选出4个与Edl突变基因连锁的多态性分子标记,利用这些标记在BC1M群体386个个体的DNA中进行基因分型,将Edl突变位点锁定在家蚕基因组nscaf2853上约390 kb的范围内,其中标记SD02和SD04分布在Edl突变位点两侧,且与该位点均相距0.5 cM,而标记SD03与Edl突变位点紧密连锁。对定位区域的基因组预测基因进行分析,初步推测家蚕Hox基因族成员Abd-A是导致Edl突变的候选基因。

In silkworm（Bombyx mori）,E group genes are a group of multiple pseudoallelic genes located on chromosome 6.Phenotypes of E group mutant include redundancy or decrease in stripes,variation in appendages,segmental malformation,organ abnormality and embryonic lethality.Study on molecular mapping of mutational gene in Bombyx mori E group mutants is beneficial to in-depth exploration of molecular regulatory mechanism of lepidopterous insect body plan.Extra-crescents and degenerated abdominal legs mutational gene（Edl） is the gene contributing to unique recessive mutation in silkworm E group mutants.Its morphological characteristics include degenerated first abdominal legs shown as residual primordia and extra crescents on dorsal part of the third abdominal segment at larval stage.In this study,based on the character of complete linkage in female silkworm individuals,we used the wild-type strain Dazao and Edl mutant to prepare BC1F population [（Dazao×Edl）♀×Edl♂] for linkage analysis and BC1M population [Edl♀×（Dazao×Edl）♂] for gene mapping.Firstly,4 poly-morphic molecular markers close to the silkworm Hox（homeotic box） gene cluster were screened.Then,genotyping was carried out on DNA of 386 individuals in BC1M population using these polymorphic markers linked with the Edl locus.Edl locus was thus delimited within a region of about 390 kb on nscaf2853 of silkworm genome.Among the 4 polymorphic markers,SD02 and SD04 was located on the two sides of Edl locus respectively,having the same genetic distance of 0.5 cM with Edl,while SD03 was closely linked with Edl locus.Analysis to predicted genes in the mapped region suggested that Bmabd-A,a member of Hox gene family in silkworm,is the candidate gene causing Edl mutation.