驯化影响下的家蚕3种抗菌肽基因的进化模式

Evolutionary Pattern of Three Bombyx mori Antimicrobial Peptide Genes Under Influence of Domestication

抗菌肽作为昆虫的先天性免疫效应因子在昆虫物种进化过程中起着至关重要的作用。测定了家蚕(Bombyx mori)和野桑蚕(Bombyxmandarina)群体的3种不同类型的抗菌肽基因DefA、CecE和MorB3的序列,通过序列核苷酸多态性分析、中性检验、溯祖模拟分析和连锁不平衡分析,发现这3种抗菌肽基因呈现不同的进化模式:DefA属于驯化过程中人工选择的靶基因;CecE是经历了驯化瓶颈效应的中性基因;MorB3的进化受遗传漂变影响。尽管进化模式不同,但家蚕的3种抗菌肽基因连锁不平衡程度均高于野桑蚕,反映家蚕经历了瓶颈效应,群体数量减小导致基因重组率降低。这些结果为理解家蚕不同抗菌肽的进化和功能提供了重要信息。

As innate immune effectors, antimicrobial peptides play crucial roles in the evolution of insect species. In this study, three different antimicrobial peptide genes, DefA, CecE and MorB3, were sequenced from both Bombyx mori and its wild relative, Bombyx mandarina. Polymorphism analyses, neutrality tests, coalescent simulation analyses and linkage disequilibrium analysis to the obtained nucleotide sequences indicated that the three genes were subject to different evo- lutionary patterns. DefA was a target gene of artificial selection during domestication, CecE was a neutral gene that had undergone domestication bottleneck effect, and the major driven force of Mort53 was genetic drift. Despite of these varied evolutionary patterns, the three genes had higher levels of linkage disequilibrium in domesticated silkworm than those in wild silkworm, indicating that domesticated silkworm had experienced a recent bottleneck effect, and decrease of population size had led to the reduction in gene recombinant rate. Our results provide important information for understanding the evolution and function of different antimicrobial peptides in domesticated silkworm.