论文部分内容阅读
目的从日本血吸虫(Schistosoma japonicum)组蛋白的基因家族进化方面入手,对其基因家族的分子系统发育、共线性关系和基因倍增模式进行分析。方法下载3种主要致病血吸虫的全基因组序列数据及外源物种基因序列,经Blastp软件比对找出组蛋白各家族基因序列,经多序列比对构建系统进化树,计算选择压力指数(Ka/Ks)。使用基因序列与基因组比对并定位,分析同源基因的共线性关系。结果日本血吸虫基因组共包含组蛋白基因38条,分为5个子家族,分布在25个scaffold上。通过进化树分析共检测到基因倍增事件34次,推定基因丢失事件17次,其中H3和H4的倍增早在血吸虫物种形成之前已经完成。日本血吸虫组蛋白的倍增机制主要是DNA复制性转座,使得组蛋白在进化保守的同时还出现了更特异性的分化,从而携带更多组蛋白密码或其他修饰信息以应对较复杂的生命周期。结论日本血吸虫的组蛋白各子家族多数倍增事件发生在从血吸虫亚洲起源后到进入非洲分化出曼氏血吸虫之前的这段时间内,表明基因倍增是血吸虫应对环境压力的重要手段。日本血吸虫的组蛋白倍增完全来自于DNA序列的复制性转座,且净化选择占主导因素,表明增强适应性的功能分化是基因进化最主要的驱动力。
Objective To analyze the molecular phylogeny, the collinearity and the gene multiplication pattern of the gene family of Schistosoma japonicum from the aspects of gene family evolution. Methods Genomic sequence data and gene sequences of exogenous species of three major pathogenic schistosomiasis strains were obtained. Blastp software was used to identify the gene sequences of histones. The phylogenetic tree was constructed by multiple sequence alignment. The selection pressure index (Ka / Ks). Using gene sequences and genome alignment and mapping, we analyzed the collinearity of homologous genes. Results The genome of Schistosoma japonicum contained a total of 38 histone genes, which were divided into 5 subfamilies and distributed on 25 scaffolds. Thirty-four times of genetic doubling events were detected by phylogenetic tree analysis, and 17 events were presumed to be genetic loss events. The doubling of H3 and H4 has been completed before schistosome species formation. The mechanism of multiplication of Schistosoma japonicum histone is mainly DNA replication transposon, which makes histone evolution more conservative and at the same time it has more specific differentiation, thus carrying more histone codons or other modification information to deal with more complex life cycle . Conclusions The majority of histone subfamilies in Schistosoma japonicum occur during the period from the origin of Schistosoma japonicum to the time before entering Schistosoma mansoni in Africa, suggesting that gene duplication is an important means of dealing with environmental stress. The histone doubling of Schistosoma japonicum is entirely due to replicative transposition of the DNA sequence, with purification options dominated, suggesting that functional differentiation that enhances accommodation is the dominant driver of gene evolution.