Institut National de Recherche Agronomique, Unité Mixte de Recherche 118, Amélioration des Plantes et Biotechnologies Végétales, BP 35327, F-35653 Le Rheu cedex, France.
Plant Cell. 2010 Jul;22(7):2253-64. doi: 10.1105/tpc.110.075986. Epub 2010 Jul 9.
Meiotic crossovers are necessary to generate balanced gametes and to increase genetic diversity. Even if crossover number is usually constrained, recent results suggest that manipulating karyotype composition could be a new way to increase crossover frequency in plants. In this study, we explored this hypothesis by analyzing the extent of crossover variation in a set of related diploid AA, allotriploid AAC, and allotetraploid AACC Brassica hybrids. We first used cytogenetic methods to describe the meiotic behavior of the different hybrids. We then combined a cytogenetic estimation of class I crossovers in the entire genome by immunolocalization of a key protein, MutL Homolog1, which forms distinct foci on meiotic chromosomes, with genetic analyses to specifically compare crossover rates between one pair of chromosomes in the different hybrids. Our results showed that the number of crossovers in the allotriploid AAC hybrid was higher than in the diploid AA hybrid. Accordingly, the allotetraploid AACC hybrid showed an intermediate behavior. We demonstrated that this increase was related to hybrid karyotype composition (diploid versus allotriploid versus allotetraploid) and that interference was maintained in the AAC hybrids. These results could provide another efficient way to manipulate recombination in traditional breeding and genetic studies.
减数分裂交叉是生成平衡配子和增加遗传多样性所必需的。即使交叉数通常受到限制，但最近的研究结果表明，操纵染色体组组成可能是增加植物中交叉频率的一种新方法。在这项研究中，我们通过分析一组相关的二倍体 AA、异源三倍体 AAC 和异源四倍体 AACC 芸薹属杂种的交叉变化程度来探索这一假设。我们首先使用细胞遗传学方法来描述不同杂种的减数分裂行为。然后，我们通过免疫定位关键蛋白 MutL Homolog1 对整个基因组中的 I 类交叉进行细胞遗传学估计，该蛋白在减数分裂染色体上形成独特的焦点，结合遗传分析，专门比较不同杂种中一对染色体之间的交叉率。我们的结果表明，异源三倍体 AAC 杂种中的交叉数高于二倍体 AA 杂种。相应地，异源四倍体 AACC 杂种表现出中间行为。我们证明这种增加与杂种染色体组组成（二倍体与异源三倍体与异源四倍体）有关，并且在 AAC 杂种中保持了干扰。这些结果可能为传统育种和遗传研究中的重组操纵提供另一种有效方法。
