State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Nanjing University, Nanjing 210093, China.
Proc Natl Acad Sci U S A. 2012 Dec 18;109(51):20992-7. doi: 10.1073/pnas.1211827110. Epub 2012 Dec 3.
The evolutionary importance of meiosis may not solely be associated with allelic shuffling caused by crossing-over but also have to do with its more immediate effects such as gene conversion. Although estimates of the crossing-over rate are often well resolved, the gene conversion rate is much less clear. In Arabidopsis, for example, next-generation sequencing approaches suggest that the two rates are about the same, which contrasts with indirect measures, these suggesting an excess of gene conversion. Here, we provide analysis of this problem by sequencing 40 F(2) Arabidopsis plants and their parents. Small gene conversion tracts, with biased gene conversion content, represent over 90% (probably nearer 99%) of all recombination events. The rate of alteration of protein sequence caused by gene conversion is over 600 times that caused by mutation. Finally, our analysis reveals recombination hot spots and unexpectedly high recombination rates near centromeres. This may be responsible for the previously unexplained pattern of high genetic diversity near Arabidopsis centromeres.
减数分裂的进化重要性可能不仅与交叉互换引起的等位基因改组有关，还与基因转换等更直接的效应有关。尽管交叉互换率的估计通常很明确，但基因转换率则不那么清楚。例如，在拟南芥中，下一代测序方法表明这两个速率大致相同，这与间接测量结果形成对比，间接测量结果表明基因转换过剩。在这里，我们通过对 40 株 F2 拟南芥植物及其亲本进行测序来分析这个问题。具有偏倚基因转换含量的小基因转换片段代表了超过 90%（可能接近 99%）的所有重组事件。基因转换引起的蛋白质序列改变率是突变引起的改变率的 600 多倍。最后，我们的分析揭示了重组热点和令人惊讶的靠近着丝粒的高重组率。这可能是造成先前未解释的拟南芥着丝粒附近高遗传多样性模式的原因。
