Mézard C
Station de Génétique et d'Amélioration des Plantes, Institut Jean-Pierre Bourgin, INRA, route de Saint-Cyr, 78026 Versailles cedex, France.
Biochem Soc Trans. 2006 Aug;34(Pt 4):531-4. doi: 10.1042/BST0340531.
Many studies have demonstrated that the distribution of meiotic crossover events along chromosomes is non-random in plants and other species with sexual reproduction. Large differences in recombination frequencies appear at several scales. On a large scale, regions of high and low rates of crossover have been found to alternate along the chromosomes in all plant species studied. High crossover rates have been reported to be correlated with several chromosome features (e.g. gene density and distance to the centromeres). However, most of these correlations cannot be extended to all plant species. Only a few plant species have been studied on a finer scale. Hotspots of meiotic recombination (i.e. DNA fragments of a few kilobases in length with a higher rate of recombination than the surrounding DNA) have been identified in maize and rice. Most of these hotspots are intragenic. In Arabidopsis thaliana, we have identified several DNA fragments (less than 5 kb in size) with genetic recombination rates at least 5 times higher than the whole-chromosome average [4.6 cM (centimorgan)/Mb], which are therefore probable hotspots for meiotic recombination. Most crossover breakpoints lie in intergenic or non-coding regions. Major efforts should be devoted to characterizing meiotic recombination at the molecular level, which should help to clarify the role of this process in genome evolution.
许多研究表明，在植物和其他有性繁殖物种中，减数分裂交叉事件沿染色体的分布是非随机的。重组频率在几个尺度上存在很大差异。在大尺度上，在所研究的所有植物物种中，高交叉率区域和低交叉率区域沿染色体交替出现。据报道，高交叉率与几个染色体特征相关（例如基因密度和到着丝粒的距离）。然而，这些相关性大多不能推广到所有植物物种。只有少数植物物种在更精细的尺度上得到了研究。在玉米和水稻中已经鉴定出减数分裂重组热点（即长度为几千碱基的DNA片段，其重组率高于周围DNA）。这些热点大多位于基因内。在拟南芥中，我们已经鉴定出几个DNA片段（大小小于5 kb），其遗传重组率至少比全染色体平均水平[4.6 cM（厘摩）/Mb]高5倍，因此可能是减数分裂重组的热点。大多数交叉断点位于基因间或非编码区域。应主要致力于在分子水平上表征减数分裂重组，这将有助于阐明这一过程在基因组进化中的作用。
