原核生物中DNA同源重组在进化中的作用

在进化机制上，虽然真核生物与原核生物有很多相似之处，但两者在重组方面存在巨大的差异。传统上认为，真核生物的进化主要是通过同源重组修改现存的遗传信息，而原核生物则主要通过水平基因转移，从远缘物种获得序列并整合到自身基因组中。近十五年来积累的群体遗传学数据表明，原核生物同源重组是常规事件，而非例外的现象。但是由于实验方法、信息处理等方面的缺憾，原核生物同源重组对进化的影响程度尚不清楚。我们的前期研究在方法学上进行了突破性的创新，有迹象显示同源重组在原核生物进化中起着重要作用，其作用强度可以达到异交哺乳动物的水平。现已收集整理六千多个菌株的全基因组数据，共覆盖近2600个种，其中157个物种可用于分析全基因组水平上的同源重组事件。本项目以大量原核生物的全基因组数据为样本，分析同源重组事件，以回答"原核生物中同源重组对进化的作用强度有多大"这一科学问题，并分析影响原核生物同源重组的因素。

Eukaryotes and prokaryotes have many similarities in evolutionary mechanism. But the two have great differences in recombination. Conventional wisdom is that eukaryotes exchange their genomic sequences through homologous recombination to evolve. Meanwhile, prokaryotes adopt the strategy of horizontal gene transfer, they get DNA sequence from not so closed related species and integrated the foreign molecular into their own genomes. In recent years, many evidences in the field of population genetics show that homologous recombination in prokaryotes has been regarded as the norm rather than the exception. Because of the defects in experimental method and theoretical basis, studies concerned about the role of homologous recombination in the evolution of prokaryotes are still in their infancy. In our preliminary study, we have collected full-genome sequences of over 6000 strains, which covered about 2600 species. Our study show that, homologous recombination play an important role in the evolutional process of bacteria. And its intensity is almost the same level as mammals with sexual reproduction. Base on abundant sequence data, we are able to analysis the homologous recombination events in full genomic level. It will contribute to find out characters of homologous recombination and universal rules in prokaryotic kingdom. And it will be helpful to understand the evolutional process of prokaryotes as a whole, as well as the role of homologous recombination in the evolution of prokaryotic genomes.