基于amy基因的中国野桑蚕遗传多样性及其与家蚕的系统发育关系

为探索中国野桑蚕Bombyx mandarina的遗传多样性及其与家蚕B. mori的系统发育关系, 采用PCR产物直接测序法（少数样本克隆测序）获得34个家蚕和野桑蚕样本淀粉酶基因amy序列片段（715 bp）。分析发现56个多态性位点, 鉴定出28种单倍型（haplotype）; 核苷酸多样性π=0.01390±0.00103, 单倍型多样度Hd=0.988±0.011。核苷酸不配对分析（mismatch analysis）和Fu’s Fs 检测表明中国野桑蚕曾发生过种群扩张。分子方差分析（AMOVA）表明, 遗野桑蚕传差异主要在种群内, 种群间和地理组群间差异不显著。聚类树上34个样本聚为3枝/3蔟, 野蚕和家蚕都不按地理区域或系统（类型）聚类, A枝由来自不同地区的野蚕和不同类型的家蚕混合构成, 并且进一步分成3个亚枝, 每一亚枝也同时包含家蚕和野蚕, B枝由3个家蚕和1个野蚕混合构成, C枝全部由来自不同地区的野蚕构成。网络分析没有发现“祖先单倍型”和优势单倍型。结果提示, 淀粉酶基因是一个多态性丰富的分子标记, 中国野桑蚕遗传多样性十分丰富, 据此推测家蚕起源于多种生态类型混杂的野桑蚕。

Genetic diversity of the wild mulberry silkworm, Bombyx mandarina, in China and its phylogenetic relationship with the domesticated silkworm, Bombyx mori, based on amy gene

Polymerase chain reaction and PCR products directly sequencing method (a few samples sequenced by cloning) were used to analyze the genetic diversity of the wild mulberry silkworm, Bombyx mandarina in China and the phylogeny of the domesticated silkworm, B. mori. A total of 715 bp nucleotides of partial amylase gene amy were sequenced in thirty-four samples from three groups of B. mandarina and four types of B. mori. Fifty-six polymorphic sites, including 28 singleton variable sites and 28 parsimony informative sites, defined 28 haplotypes. The nucleotides diversity (π) was 0. 01390 ±0.00103 and the haplotype diversity (Hd) was 0. 988 ±0.011. Mismatch analysis and Fu' s Fs test revealed the population expansion of B. mori in the past. Analysis of molecular variance (AMOVA) suggested that genetic variance mostly existed within populations and accounted for 82. 63% of total variation. Variance between population and population-groups was not significant. The phylogenetic analysis indicated that three clusters were formed by the thirty-four samples analyzed. Cluster A consisted of B. mandarina from different regions and B. mori from different types, which was further divided into three sub-clusters. Cluster B consisted of three B. mori and one B. mandarina, while cluster C consisted of B. mandarina from different regions only. There is no ancestor haplotype and dominant haplotype in the median-joining network. The results suggest that: (1) the amy gene is a molecular marker with rich diversity in silkworms; (2) there is great genetic diversity within B. mandarina population in China; and (3) the domesticated silkworm may be domesticated from multi-typed B. mandarina, which supports the theory of multiple origins from a variety of B. mandarina.