Case Andrea L, Finseth Findley R, Barr Camille M, Fishman Lila
Department of Biological Sciences, Kent State University, Kent, OH 44242, USA
Division of Biological Sciences, University of Montana, Missoula, MT 59812, USA.
Proc Biol Sci. 2016 Sep 14;283(1838). doi: 10.1098/rspb.2016.1493.
Intraspecific coevolution between selfish elements and suppressors may promote interspecific hybrid incompatibility, but evidence of this process is rare. Here, we use genomic data to test alternative models for the evolution of cytonuclear hybrid male sterility in Mimulus In hybrids between Iron Mountain (IM) Mimulus guttatus × Mimulus nasutus, two tightly linked M. guttatus alleles (Rf1/Rf2) each restore male fertility by suppressing a local mitochondrial male-sterility gene (IM-CMS). Unlike neutral models for the evolution of hybrid incompatibility loci, selfish evolution predicts that the Rf alleles experienced strong selection in the presence of IM-CMS. Using whole-genome sequences, we compared patterns of population-genetic variation in Rf at IM to a neighbouring population that lacks IM-CMS. Consistent with local selection in the presence of IM-CMS, the Rf region shows elevated FST, high local linkage disequilibrium and a distinct haplotype structure at IM, but not at Cone Peak (CP), suggesting a recent sweep in the presence of IM-CMS. In both populations, Rf2 exhibited lower polymorphism than other regions, but the low-diversity outliers were different between CP and IM. Our results confirm theoretical predictions of ubiquitous cytonuclear conflict in plants and provide a population-genetic mechanism for the evolution of a common form of hybrid incompatibility.
自私元件与抑制因子之间的种内协同进化可能会促进种间杂交不亲和性，但这一过程的证据很少。在这里，我们利用基因组数据来检验报春花属植物细胞核质杂种雄性不育进化的替代模型。在铁山（IM）黄花九轮草×鼻花的杂种中，两个紧密连锁的黄花九轮草等位基因（Rf1/Rf2）通过抑制一个局部线粒体雄性不育基因（IM-CMS）来恢复雄性育性。与杂种不亲和性位点进化的中性模型不同，自私进化预测Rf等位基因在存在IM-CMS的情况下经历了强烈选择。利用全基因组序列，我们将IM处Rf的群体遗传变异模式与缺乏IM-CMS的相邻群体进行了比较。与在存在IM-CMS时的局部选择一致，Rf区域在IM处显示出升高的FST、高局部连锁不平衡和独特的单倍型结构，但在锥峰（CP）处没有，这表明在存在IM-CMS时最近发生了一次扫荡。在两个群体中，Rf2的多态性都低于其他区域，但CP和IM的低多样性异常值不同。我们的结果证实了植物中普遍存在的细胞核质冲突的理论预测，并为一种常见的杂种不亲和形式的进化提供了一种群体遗传机制。
