Gene conversion drives within genic sequences: Concerted evolution of ribosomal RNA genes in bacteria and archaea
Gene conversion drives within genic sequences: Concerted evolution of ribosomal RNA genes in bacteria and archaea
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DOI：
10.1007/s002390010093
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发表时间：
2000-10-01
影响因子：
3.9
通讯作者：
Liao, DQ
中科院分区：
文献类型：
--
作者：
Liao, DQ
一个核糖体RNA基因家族的多个拷贝经历了协调一致的进化，使得所有基因拷贝的序列在一个物种内几乎是相同的，尽管它们在物种之间通常是不同的。在真核生物中，基因转换和不平等杂交是提出的串联重复序列协同进化的机制，而分散的基因则通过基因转换而均匀化。然而，多拷贝、通常分散的原核rRNA基因的均质机制尚不清楚。在这里，我们比较了12个具有多个拷贝rRNA基因的原核生物基因组中多个旁系rRNA基因的序列。在基因组中，假定的序列转换束遍布每个单独rRNA基因的整个长度及其紧邻的侧翼。单个转化事件仅转化一个短序列束，而转化伙伴可以是基因组内的任何同源基因。有趣的是，基因序列的分化速度比它们的侧翼序列慢得多。此外，基因组背景和操纵子组织不影响rRNA基因的均质化。因此，基因转换是细菌rRNA基因协同进化的基础，这通常发生在基因序列内，而侧翼区域的均匀化可能是由与基因序列的共转换引起的。
Multiple copies of a given ribosomal RNA gene family undergo concerted evolution such that sequences of all gene copies are virtually identical within a species although they diverge normally between species. In eukaryotes, gene conversion and unequal crossing over are the proposed mechanisms for concerted evolution of tandemly repeated sequences, whereas dispersed genes are homogenized by gene conversion. However, the homogenization mechanisms for multiple-copy, normally dispersed, prokaryotic rRNA genes are not well understood. Here we compared the sequences of multiple paralogous rRNA genes within a genome in 12 prokaryotic organisms that have multiple copies of the rRNA genes. Within a genome, putative sequence conversion tracts were found throughout the entire length of each individual rRNA genes and their immediate flanks. Individual conversion events convert only a short sequence tract, and the conversion partners can be any paralogous genes within the genome. Interestingly, the genic sequences undergo much slower divergence than their flanking sequences. Moreover, genomic context and operon organization do not affect rRNA gene homogenization. Thus, gene conversion underlies concerted evolution of bacterial rRNA genes, which normally occurs within genic sequences, and homogenization of flanking regions may result from co-conversion with the genic sequence.