Garner Austin G, Kenney Amanda M, Fishman Lila, Sweigart Andrea L
Department of Genetics, University of Georgia, Athens, GA, 30602, USA.
Department of Biological Sciences, St Edwards University, Austin, TX, 78704, USA.
New Phytol. 2016 Jul;211(1):319-31. doi: 10.1111/nph.13897. Epub 2016 Feb 29.
In flowering plants, F1 hybrid seed lethality is a common outcome of crosses between closely related diploid species, but the genetic basis of this early-acting and potentially widespread form of postzygotic reproductive isolation is largely unknown. We intercrossed two closely related species of monkeyflower, Mimulus guttatus and Mimulus tilingii, to characterize the mechanisms and strength of postzygotic reproductive isolation. Then, using a reciprocal backcross design, we performed high-resolution genetic mapping to determine the genetic architecture of hybrid seed lethality and directly test for loci with parent-of-origin effects. We found that F1 hybrid seed lethality is an exceptionally strong isolating barrier between Mimulus species, with reciprocal crosses producing < 1% viable seeds. This form of postzygotic reproductive isolation appears to be highly polygenic, indicating that multiple incompatibility loci have accumulated rapidly between these closely related Mimulus species. It is also primarily caused by genetic loci with parent-of-origin effects, suggesting a possible role for imprinted genes in the evolution of Mimulus hybrid seed lethality. Our findings suggest that divergence in loci with parent-of-origin effects, which is probably driven by genomic coevolution within lineages, might be an important source of hybrid incompatibilities between flowering plant species.
在开花植物中，F1杂种种子致死是亲缘关系较近的二倍体物种杂交的常见结果，但这种早期起作用且可能广泛存在的合子后生殖隔离形式的遗传基础在很大程度上尚不清楚。我们使两个亲缘关系较近的沟酸浆属植物物种——斑点沟酸浆（Mimulus guttatus）和蒂氏沟酸浆（Mimulus tilingii）进行种间杂交，以表征合子后生殖隔离的机制和强度。然后，我们采用正反交回交设计，进行高分辨率遗传图谱绘制，以确定杂种种子致死的遗传结构，并直接检测具有亲本效应的基因座。我们发现，F1杂种种子致死是沟酸浆属物种之间一种异常强大的隔离屏障，正反交产生的可存活种子均不到1%。这种合子后生殖隔离形式似乎是高度多基因的，这表明在这些亲缘关系较近的沟酸浆属物种之间，多个不相容基因座迅速积累。它也主要由具有亲本效应的基因座引起，这表明印记基因可能在沟酸浆属杂种种子致死的进化中发挥作用。我们的研究结果表明，可能由谱系内基因组共同进化驱动的具有亲本效应的基因座的分歧，可能是开花植物物种间杂种不相容性的一个重要来源。
