Mechanisms of Transmission Ratio Distortion at Hybrid Sterility Loci Within and Between Mimulus Species.
Mechanisms of Transmission Ratio Distortion at Hybrid Sterility Loci Within and Between Mimulus Species.
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DOI：
10.1534/g3.117.300148
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发表时间：
2017-11-06
期刊：
影响因子：
--
通讯作者：
Sweigart AL
中科院分区：
文献类型：
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作者：
Kerwin RE;Sweigart AL
杂种不亲和性是基因组分化的一个常见相关因素，也是生殖隔离的一个潜在重要因素。然而，我们还没有详细了解杂交不亲和位点如何在其原生物种中发挥作用和进化，或者为什么它们在杂交种中功能失调。在这里，我们探讨了这些问题的一个充分研究，两个位点之间的杂交雄性不育1（hms 1）和杂交雄性不育2（hms 2）在密切相关的黄色monkeyflower物种Mimulus guttatus和M。鼻骨。通过与渐渗系（ILs）进行相互回交，我们发现了hms 1-hms 2不亲和性配子表达的证据。然而，令人惊讶的是，在hms 1的杂交传递率并不反映这种不相容性，这表明额外的机制抵消配子不育的影响。实际上，我们的回交实验显示了对M的杂交传递偏向。guttatus通过花粉和胚珠，当hms 2是M. nasutus等位基因相比之下，我们发现很少的证据表明，在M内的交叉hms 1传输偏差。guttatus，在这个位点没有提供自私进化的迹象。虽然我们还没有足够的遗传分辨率，以确定是否混合不育和传输比失真（TRD）映射到相同的位点，我们初步的精细映射揭示了一个遗传上独立的混合致死系统，涉及至少两个位点与hms 1。TRD在hms 1和hms 2的这种精细解剖提供了对密切相关的Mimulus物种之间的基因组分化的深入了解，并揭示了杂交功能障碍的多种机制。
Hybrid incompatibilities are a common correlate of genomic divergence and a potentially important contributor to reproductive isolation. However, we do not yet have a detailed understanding of how hybrid incompatibility loci function and evolve within their native species, or why they are dysfunctional in hybrids. Here, we explore these issues for a well-studied, two-locus hybrid incompatibility between hybrid male sterility 1 (hms1) and hybrid male sterility 2 (hms2) in the closely related yellow monkeyflower species Mimulus guttatus and M. nasutus. By performing reciprocal backcrosses with introgression lines (ILs), we find evidence for gametic expression of the hms1-hms2 incompatibility. Surprisingly, however, hybrid transmission ratios at hms1 do not reflect this incompatibility, suggesting that additional mechanisms counteract the effects of gametic sterility. Indeed, our backcross experiment shows hybrid transmission bias toward M. guttatus through both pollen and ovules, an effect that is particularly strong when hms2 is homozygous for M. nasutus alleles. In contrast, we find little evidence for hms1 transmission bias in crosses within M. guttatus, providing no indication of selfish evolution at this locus. Although we do not yet have sufficient genetic resolution to determine if hybrid sterility and transmission ratio distortion (TRD) map to the same loci, our preliminary fine-mapping uncovers a genetically independent hybrid lethality system involving at least two loci linked to hms1. This fine-scale dissection of TRD at hms1 and hms2 provides insight into genomic differentiation between closely related Mimulus species and reveals multiple mechanisms of hybrid dysfunction.