Groningen Institute for Evolutionary Life Sciences, Faculty of Science and Engineering, University of Groningen, Groningen, the Netherlands.
Insect Sci. 2022 Oct;29(5):1470-1482. doi: 10.1111/1744-7917.13017. Epub 2022 Mar 15.
Sex-determination mechanisms evolve rapidly and vary between species. Occasionally, polymorphic systems are found, like in the housefly. Studying the dynamics and stability of such systems can provide a better understanding of the evolution of sex-determination systems. In the housefly, dominant male-determining loci (M) can lie not only on the Y chromosome (M ), but also on autosomes (M ) or the X chromosome (M ). M enforces male development by inhibiting the female-determining gene transformer (tra). A mutant tra allele, tra , is insensitive to M and is a dominant female determiner. M prevails at high latitudes and polymorphic M loci together with tra at low latitudes. To get more insight into the stability and frequencies of these sex determiners with mutually exclusive dominance, we investigated 5 regional Spanish populations. We found strong variation among populations. Two populations with hemizygous M were found, 2 contained homozygous M with additional hemizygous M and M in 1 population. One population contained homozygous and hemizygous M with additionally hemizygous M . All females in populations with homozygous M, had tra , whereas no tra was found in populations without homozygous M. Our results indicate locally stable systems may either harbor a single hemizygous M and no tra , corresponding to a male heterogametic system, or homozygous and/or multiple M and heterozygous tra , reminiscent of a female heterogametic system. They support that M loci can accumulate in the presence of a dominant female determiner. Limited migration between populations may contribute to the stability of these systems.
性别决定机制在物种间迅速进化且存在差异。偶尔会发现多态系统，例如家蝇。研究这些系统的动态和稳定性可以更好地理解性别决定系统的进化。在家蝇中，显性雄性决定基因座（M）不仅存在于 Y 染色体（M）上，还存在于常染色体（M）或 X 染色体（M）上。M 通过抑制雌性决定基因转化器（tra）来强制雄性发育。突变的 tra 等位基因 tra 对 M 不敏感，是显性雌性决定基因。M 在高纬度地区占优势，而多态 M 基因座与 tra 在低纬度地区共存。为了更深入地了解这些具有互斥显性的性别决定基因的稳定性和频率，我们研究了 5 个西班牙地区种群。我们发现种群之间存在强烈的差异。发现了两个具有半合子 M 的种群，两个种群含有纯合子 M，另外还有半合子 M 和 M，1 个种群含有纯合子和半合子 M，另外还有半合子 M。在含有纯合子 M 的种群中，所有雌性都具有 tra ，而在没有纯合子 M 的种群中则没有发现 tra。我们的结果表明，局部稳定的系统可能只含有单个半合子 M 和无 tra，对应于雄性异配子系统，或者含有纯合子和/或多个 M 和杂合子 tra，类似于雌性异配子系统。它们支持 M 基因座可以在存在显性雌性决定基因的情况下积累。种群之间有限的迁移可能有助于这些系统的稳定性。
