Department of Ecology, Faculty of Science, Charles University, Viničná 7, Prague, Czech Republic.
Leibniz-Institute of Freshwater Ecology and Inland Fisheries - IGB (Forschungsverbund Berlin), Müggelseedamm 301, 12587 Berlin, Germany.
Philos Trans R Soc Lond B Biol Sci. 2021 Sep 13;376(1833):20200097. doi: 10.1098/rstb.2020.0097. Epub 2021 Jul 26.
Until recently, the field of sex chromosome evolution has been dominated by the canonical unidirectional scenario, first developed by Muller in 1918. This model postulates that sex chromosomes emerge from autosomes by acquiring a sex-determining locus. Recombination reduction then expands outwards from this locus, to maintain its linkage with sexually antagonistic/advantageous alleles, resulting in Y or W degeneration and potentially culminating in their disappearance. Based mostly on empirical vertebrate research, we challenge and expand each conceptual step of this canonical model and present observations by numerous experts in two parts of a theme issue of We suggest that greater theoretical and empirical insights into the events at the origins of sex-determining genes (rewiring of the gonadal differentiation networks), and a better understanding of the evolutionary forces responsible for recombination suppression are required. Among others, crucial questions are: Why do sex chromosome differentiation rates and the evolution of gene dose regulatory mechanisms between male versus female heterogametic systems not follow earlier theory? Why do several lineages not have sex chromosomes? And: What are the consequences of the presence of (differentiated) sex chromosomes for individual fitness, evolvability, hybridization and diversification? We conclude that the classical scenario appears too reductionistic. Instead of being unidirectional, we show that sex chromosome evolution is more complex than previously anticipated and principally forms networks, interconnected to potentially endless outcomes with restarts, deletions and additions of new genomic material. This article is part of the theme issue 'Challenging the paradigm in sex chromosome evolution: empirical and theoretical insights with a focus on vertebrates (Part II)'.
直到最近，性染色体进化领域一直由 1918 年 Muller 首次提出的经典单向情景主导。该模型假设性染色体通过获得性别决定基因座从常染色体中出现。然后，重组减少从该基因座向外扩展，以维持其与性拮抗/有利等位基因的连锁，导致 Y 或 W 退化，并可能最终导致它们消失。主要基于经验性的脊椎动物研究，我们挑战并扩展了这个经典模型的每个概念步骤，并在主题问题的两部分中呈现了众多专家的观察结果。我们认为，需要对性别决定基因起源事件（性腺分化网络的重新布线）有更深入的理论和经验见解，以及对负责重组抑制的进化力量有更好的理解。其中，关键问题是：为什么性染色体分化速度和雄性与雌性异型配子系统之间的基因剂量调节机制的进化不符合早期理论？为什么有些谱系没有性染色体？还有：存在（分化的）性染色体对个体适应性、可进化性、杂交和多样化有什么影响？我们得出结论，经典情景似乎过于简化。我们表明，性染色体进化比以前预期的更复杂，主要形成网络，与潜在的无限结果相互连接，具有重新启动、删除和添加新基因组物质。本文是主题问题“挑战性染色体进化范式：以脊椎动物为重点的经验和理论见解（第二部分）”的一部分。
