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首页> 外文期刊>Journal of bacteriology >Gene Conversion Tracts Associated with Crossovers in Rhizobium etli
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Gene Conversion Tracts Associated with Crossovers in Rhizobium etli

机译：根瘤菌中与交叉相关的基因转化途径

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Gene conversion has been defined as the nonreciprocal transfer of information between homologous sequences. Despite its broad interest for genome evolution, the occurrence of this mechanism in bacteria has been difficult to ascertain due to the possible occurrence of multiple crossover events that would mimic gene conversion. In this work, we employ a novel system, based on cointegrate formation, to isolate gene conversion events associated with crossovers in the nitrogen-fixing bacterium Rhizobium etli. In this system, selection is applied only for cointegrate formation, with gene conversions being detected as unselected events. This minimizes the likelihood of multiple crossovers. To track the extent and architecture of gene conversions, evenly spaced nucleotide changes were made in one of the nitrogenase structural genes (nifH), introducing unique sites for different restriction endonucleases. Our results show that (i) crossover events were almost invariably accompanied by a gene conversion event occurring nearby; (ii) gene conversion events ranged in size from 150 bp to 800 bp; (iii) gene conversion events displayed a strong bias, favoring the preservation of incoming sequences; (iv) even small amounts of sequence divergence had a strong effect on recombination frequency; and (v) the MutS mismatch repair system plays an important role in determining the length of gene conversion segments. A detailed analysis of the architecture of the conversion events suggests that multiple crossovers are an unlikely alternative for their generation. Our results are better explained as the product of true gene conversions occurring under the double-strand break repair model for recombination.
机译：基因转换已被定义为同源序列之间信息的不可逆转移。尽管它对基因组进化有着广泛的兴趣，但是由于可能会发生模仿基因转化的多重交换事件，因此很难确定细菌中这种机制的发生。在这项工作中，我们采用一种基于共积分形成的新系统，以分离与固氮细菌 Rhizobium etli 中的交叉相关的基因转化事件。在该系统中，选择仅用于共整合的形成，而将基因转化检测为未选择的事件。这样可以最大程度地减少多次交叉的可能性。为了跟踪基因转化的程度和结构，在其中一个固氮酶结构基因（ nifH ）中进行了等距核苷酸变化，为不同的限制性内切核酸酶引入了独特的位点。我们的结果表明：（i）交换事件几乎总是伴随着附近发生的基因转化事件; （ii）基因转化事件的大小范围为150 bp至800 bp; （iii）基因转化事件表现出强烈的偏见，有利于保存输入序列; （iv）即使很小的序列差异也对重组频率有很强的影响; （v）MutS错配修复系统在确定基因转化区段的长度中起重要作用。对转换事件的体系结构的详细分析表明，多个交叉不太可能替代它们的生成。我们的结果可以更好地解释为在重组的双链断裂修复模型下发生的真正基因转化的产物。

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