Center for Reproductive Medicine, Shandong University, National Research Center for Assisted Reproductive Technology and Reproductive Genetics, Key Laboratory of Reproductive Endocrinology of Ministry of Education, Jinan, Shandong 250001, China.
Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA; Program for Evolutionary Dynamics, Harvard University, Cambridge, MA 02138, USA.
Cell. 2019 Apr 4;177(2):326-338.e16. doi: 10.1016/j.cell.2019.02.021. Epub 2019 Mar 14.
Crossing over is a nearly universal feature of sexual reproduction. Here, analysis of crossover numbers on a per-chromosome and per-nucleus basis reveals a fundamental, evolutionarily conserved feature of meiosis: within individual nuclei, crossover frequencies covary across different chromosomes. This effect results from per-nucleus covariation of chromosome axis lengths. Crossovers can promote evolutionary adaptation. However, the benefit of creating favorable new allelic combinations must outweigh the cost of disrupting existing favorable combinations. Covariation concomitantly increases the frequencies of gametes with especially high, or especially low, numbers of crossovers, and thus might concomitantly enhance the benefits of crossing over while reducing its costs. A four-locus population genetic model suggests that such an effect can pertain in situations where the environment fluctuates: hyper-crossover gametes are advantageous when the environment changes while hypo-crossover gametes are advantageous in periods of environmental stasis. These findings reveal a new feature of the basic meiotic program and suggest a possible adaptive advantage.
交叉是有性生殖的一个普遍特征。在这里，基于每条染色体和每个细胞核对交叉数的分析揭示了减数分裂的一个基本的、进化上保守的特征：在单个细胞核内，不同染色体上的交叉频率是相互关联的。这种效应源于染色体轴长度在每个细胞核内的共变。交叉可以促进进化适应。然而，创造有利的新等位基因组合的好处必须超过破坏现有有利组合的成本。共变同时增加了具有特别高或特别低交叉数的配子的频率，因此可能同时增强交叉的好处，同时降低其成本。一个四基因座群体遗传模型表明，在环境波动的情况下，这种效应可能存在：当环境发生变化时，超交叉配子是有利的，而在环境稳定期，低交叉配子是有利的。这些发现揭示了基本减数分裂程序的一个新特征，并暗示了可能的适应性优势。
