Divergence in gene expression regulation is common between closely related species and may give rise to incompatibilities in their hybrid progeny. In this study, we investigated the relationship between regulatory evolution within species and reproductive isolation between species. We focused on a well-studied case of hybrid sterility between two closely related yellow monkeyflower species, Mimulus guttatus and Mimulus nasutus, that is caused by two epistatic loci, hybrid male sterility 1 (hms1) and hybrid male sterility 2 (hms2). We compared genome-wide transcript abundance across male and female reproductive tissues (i.e., stamens and carpels) from four genotypes: M. guttatus, M. nasutus, and sterile and fertile progeny from an advanced M. nasutus–M. guttatus introgression line carrying the hms1–hms2 incompatibility. We observed substantial variation in transcript abundance between M. guttatus and M. nasutus, including distinct but overlapping patterns of tissue-biased expression, providing evidence for regulatory divergence between these species. We also found rampant genome-wide misexpression, but only in the affected tissues (i.e., stamens) of sterile introgression hybrids carrying incompatible alleles at hms1 and hms2. Examining patterns of allele-specific expression in sterile and fertile introgression hybrids, we found evidence for interspecific divergence in cis- and trans-regulation, including compensatory cis–trans mutations likely to be driven by stabilizing selection. Nevertheless, species divergence in gene regulatory networks cannot explain the vast majority of the gene misexpression we observe in Mimulus introgression hybrids, which instead likely manifests as a downstream consequence of sterility itself.

中文翻译：

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杂种不育而不是调节差异引起的杂种（Monkeyflower）渗入系中的猖amp错误表达。

在密切相关的物种之间，基因表达调控的差异是常见的，并且可能导致其杂交后代不相容。在这项研究中，我们调查了物种内部的调节进化与物种之间的生殖隔离之间的关系。我们重点研究了两个密切相关的黄色黄花物种Migurus guttatus和Mimulus nasutus之间的杂交不育问题，该案例由两个上位性位点杂交雄性不育1（hms1）和杂交雄性不育2（hms2）引起。我们比较了四种基因型的男性和女性生殖组织（雄蕊和心皮）的全基因组转录本丰度：M. guttatus，M。nasutus以及来自先进的M. nasutus – guttatus渗入系的不育和可育后代携带hms1–hms2不兼容。我们观察到M. guttatus和M. nasutus之间的转录丰度有很大变化，包括组织偏向表达的不同但重叠的模式，为这些物种之间的调控差异提供了证据。我们还发现了全基因组普遍的错误表达，但仅在受影响的组织（即雄蕊）的无菌渗入杂种中携带了在hms1和hms2具有不相容等位基因的杂种。在无菌和能育的渗入杂种中检查等位基因特异性表达的模式，我们发现了顺式和反式调节中种间差异的证据，包括可能由稳定选择驱动的补偿性顺式-反式突变。然而，基因调控网络中的物种差异不能解释我们在Mimulus渗入杂种中观察到的绝大多数基因表达错误，而这很可能表现为不育本身的下游结果。