Rice William R, Gavrilets Sergey, Friberg Urban
Department of Ecology, Evolution, and Marine Biology, University of California Santa Barbara, Santa Barbara, CA, USA.
PLoS Genet. 2008 Dec;4(12):e1000313. doi: 10.1371/journal.pgen.1000313. Epub 2008 Dec 19.
Genomic conflict is perplexing because it causes the fitness of a species to decline rather than improve. Many diverse forms of genomic conflict have been identified, but this extant tally may be incomplete. Here, we show that the unusual characteristics of the sex chromosomes can, in principle, lead to a previously unappreciated form of sexual genomic conflict. The phenomenon occurs because there is selection in the heterogametic sex for sex-linked mutations that harm the sex of offspring that does not carry them, whenever there is competition among siblings. This harmful phenotype can be expressed as an antagonistic green-beard effect that is mediated by epigenetic parental effects, parental investment, and/or interactions among siblings. We call this form of genomic conflict sexually antagonistic "zygotic drive", because it is functionally equivalent to meiotic drive, except that it operates during the zygotic and postzygotic stages of the life cycle rather than the meiotic and gametic stages. A combination of mathematical modeling and a survey of empirical studies is used to show that sexually antagonistic zygotic drive is feasible, likely to be widespread in nature, and that it can promote a genetic "arms race" between the homo- and heteromorphic sex chromosomes. This new category of genomic conflict has the potential to strongly influence other fundamental evolutionary processes, such as speciation and the degeneration of the Y and W sex chromosomes. It also fosters a new genetic hypothesis for the evolution of enigmatic fitness-reducing traits like the high frequency of spontaneous abortion, sterility, and homosexuality observed in humans.
基因组冲突令人困惑，因为它会导致一个物种的适应性下降而非提高。人们已经识别出许多不同形式的基因组冲突，但目前已知的这些可能并不完整。在此，我们表明，性染色体的独特特征原则上可能导致一种此前未被认识到的性基因组冲突形式。这种现象之所以会出现，是因为在异配性别中，当同胞之间存在竞争时，对于那些会伤害不携带这些突变的后代性别的性连锁突变存在选择作用。这种有害表型可以表现为一种由表观遗传亲代效应、亲代投资和/或同胞间相互作用介导的拮抗绿胡须效应。我们将这种基因组冲突形式称为性拮抗“合子驱动”，因为它在功能上等同于减数分裂驱动，只是它发生在生命周期中的合子和胚后阶段，而非减数分裂和配子阶段。通过数学建模与实证研究调查相结合的方法，我们证明性拮抗合子驱动是可行的，很可能在自然界广泛存在，并能促进同形和异形性染色体之间的遗传“军备竞赛”。这一新的基因组冲突类别有可能强烈影响其他基本的进化过程，比如物种形成以及Y和W性染色体的退化现象。它还为诸如人类中观察到的高自发流产率、不育和同性恋等神秘的适应性降低性状的进化提出了一个新的遗传学假说。
