Departamento de Sistemas y Recursos Forestales, Centro de Investigación Forestal, CIFOR-INIA, Carretera de La Coruña, ES-28040 Madrid, Spain.
BMC Evol Biol. 2010 Jan 25;10:22. doi: 10.1186/1471-2148-10-22.
Despite its role as a generator of haplotypic variation, little is known about how the rates of recombination evolve across taxa. Recombination is a very labile force, susceptible to evolutionary and life trait related processes, which have also been correlated with general levels of genetic diversity. For example, in plants, it has been shown that long-lived outcrossing taxa, such as trees, have higher heterozygosity (He) at SSRs and allozymes than selfing or annual species. However, some of these tree taxa have surprisingly low levels of nucleotide diversity at the DNA sequence level, which points to recombination as a potential generator of genetic diversity in these organisms. In this study, we examine how genome-wide and within-gene rates of recombination evolve across plant taxa, determine whether such rates are influenced by the life-form adopted by species, and evaluate if higher genome-wide rates of recombination translate into higher He values, especially in trees.
Estimates of genome-wide (cM/Mb) recombination rates from 81 higher plants showed a significant phylogenetic signal. The use of different comparative phylogenetic models demonstrated that there is a positive correlation between recombination rate and He (0.83 +/- 0.29), and that trees have higher rates of genome-wide recombination than short-lived herbs and shrubs. A significant taxonomic component was further made evident by our models, as conifers exhibited lower recombination rates than angiosperms. This trend was also found at the within-gene level.
Altogether, our results illustrate how both common ancestry and life-history traits have to be taken into account for understanding the evolution of genetic diversity and genomic rates of recombination across plant species, and highlight the relevance of species life forms to explain general levels of diversity and recombination.
尽管重组作为单倍型变异的产生因素之一，但人们对其在不同分类群中的重组率演变知之甚少。重组是一种非常不稳定的力量，容易受到进化和与生活特征相关的过程的影响，这些过程也与遗传多样性的总体水平相关。例如，在植物中，已经表明，长寿命异交的分类群，如树木，在 SSR 和同工酶中的杂合度（He）比自交或一年生物种更高。然而，这些树分类群中的一些具有令人惊讶的低 DNA 序列水平的核苷酸多样性，这表明重组是这些生物遗传多样性的潜在产生因素。在这项研究中，我们研究了重组在植物分类群中的全基因组和基因内速率如何演变，确定这些速率是否受到物种采用的生活形式的影响，并评估更高的全基因组重组率是否转化为更高的 He 值，尤其是在树木中。
从 81 种高等植物中估计的全基因组（cM/Mb）重组率显示出显著的系统发育信号。使用不同的比较系统发育模型表明，重组率与 He 之间存在正相关（0.83 +/- 0.29），并且树木的全基因组重组率高于短命的草本植物和灌木。我们的模型进一步证明了一个显著的分类学组成部分，因为针叶树的重组率低于被子植物。这种趋势在基因内水平也得到了发现。
总的来说，我们的结果说明了共同祖先和生活史特征如何必须被考虑在内，以理解遗传多样性和全基因组重组率在植物物种中的演变，并强调了物种生活形式对解释多样性和重组的一般水平的相关性。
