Liénard Marjorie A, Araripe Luciana O, Hartl Daniel L
Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138; Department of Biology, Lund University, 22362 Lund, Sweden
Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138;
Proc Natl Acad Sci U S A. 2016 Jul 19;113(29):E4200-7. doi: 10.1073/pnas.1608337113. Epub 2016 Jun 29.
Crosses between closely related animal species often result in male hybrids that are sterile, and the molecular and functional basis of genetic factors for hybrid male sterility is of great interest. Here, we report a molecular and functional analysis of HMS1, a region of 9.2 kb in chromosome 3 of Drosophila mauritiana, which results in virtually complete hybrid male sterility when homozygous in the genetic background of sibling species Drosophila simulans. The HMS1 region contains two strong candidate genes for the genetic incompatibility, agt and Taf1 Both encode unrelated DNA-binding proteins, agt for an alkyl-cysteine-S-alkyltransferase and Taf1 for a subunit of transcription factor TFIID that serves as a multifunctional transcriptional regulator. The contribution of each gene to hybrid male sterility was assessed by means of germ-line transformation, with constructs containing complete agt and Taf1 genomic sequences as well as various chimeric constructs. Both agt and Taf1 contribute about equally to HMS1 hybrid male sterility. Transgenes containing either locus rescue sterility in about one-half of the males, and among fertile males the number of offspring is in the normal range. This finding suggests compensatory proliferation of the rescued, nondysfunctional germ cells. Results with chimeric transgenes imply that the hybrid incompatibilities result from interactions among nucleotide differences residing along both agt and Taf1 Our results challenge a number of preliminary generalizations about the molecular and functional basis of hybrid male sterility, and strongly reinforce the role of DNA-binding proteins as a class of genes contributing to the maintenance of postzygotic reproductive isolation.
亲缘关系较近的动物物种之间杂交，常常会导致雄性杂交后代不育，而杂交雄性不育的遗传因素的分子和功能基础备受关注。在此，我们报告了对HMS1的分子和功能分析，HMS1位于毛里求斯果蝇3号染色体上，长度为9.2 kb，当在同胞物种拟果蝇的遗传背景中纯合时，会导致几乎完全的杂交雄性不育。HMS1区域包含两个与遗传不相容性相关的强候选基因，即agt和Taf1。二者都编码不相关的DNA结合蛋白，agt编码一种烷基半胱氨酸-S-烷基转移酶，Taf1编码转录因子TFIID的一个亚基，该亚基作为多功能转录调节因子。通过生殖系转化，利用包含完整agt和Taf1基因组序列的构建体以及各种嵌合构建体，评估了每个基因对杂交雄性不育的贡献。agt和Taf1对HMS1杂交雄性不育的贡献大致相同。含有任一基因座的转基因在大约一半的雄性中挽救了不育状态，在可育雄性中，后代数量处于正常范围。这一发现表明被挽救的、无功能异常的生殖细胞发生了代偿性增殖。嵌合转基因的结果表明，杂交不相容性是由agt和Taf1沿线的核苷酸差异之间的相互作用导致的。我们的结果对一些关于杂交雄性不育分子和功能基础的初步概括提出了挑战，并有力地强化了DNA结合蛋白作为一类有助于维持合子后生殖隔离的基因的作用。
