Jia L-Y, Xiao J-H, Xiong T-L, Niu L-M, Huang D-W
Key Laboratory of Zoological Systematics and Evolution, Institute of Zoology, Chinese Academy of Sciences, Beijing, China.
Environment and Plant Protection Institute, Chinese Academy of Tropical Agricultural Sciences, Danzhou, Hainan, China.
Insect Mol Biol. 2016 Jun;25(3):191-201. doi: 10.1111/imb.12210. Epub 2016 Jan 8.
Transformer (tra) is the key gene that turns on the sex-determination cascade in Drosophila melanogaster and in some other insects. The honeybee Apis mellifera has two duplicates of tra, one of which (complementary sex determiner, csd) is the primary signal for complementary sex-determination (CSD), regulating the other duplicate (feminizer). Two tra duplicates have been found in some other hymenopteran species, resulting in the assumption that a single ancestral duplication of tra took place in the Hymenoptera. Here, we searched for tra homologues and pseudogenes in the Hymenoptera, focusing on five newly published hymenopteran genomes. We found three tra copies in the fig wasp Ceratosolen solmsi. Further evolutionary and expression analyses also showed that the two duplicates (Csoltra-B and Csoltra-C) are under positive selection, and have female-specific expression, suggesting possible sex-related functions. Moreover, Aculeata species exhibit many pseudogenes generated by lineage-specific duplications. We conclude that phylogenetic reconstruction and pseudogene screening provide novel evidence supporting the hypothesis of independent duplications rather an ancestral origin of multiple tra paralogues in the Hymenoptera. The case of C. solmsi is the first example of a non-CSD species with duplicated tra, contrary to the previous assumption that derived tra paralogues function as the CSD locus.
Transformer（tra）是开启黑腹果蝇和其他一些昆虫性别决定级联反应的关键基因。蜜蜂（Apis mellifera）有两个tra的副本，其中一个（互补性别决定因子，csd）是互补性别决定（CSD）的主要信号，调控另一个副本（雌性化因子）。在其他一些膜翅目物种中也发现了两个tra副本，这导致人们推测tra在膜翅目中发生了一次单一的祖先复制。在这里，我们在膜翅目中寻找tra同源物和假基因，重点关注五个新发表的膜翅目基因组。我们在榕小蜂（Ceratosolen solmsi）中发现了三个tra副本。进一步的进化和表达分析还表明，这两个副本（Csoltra-B和Csoltra-C）受到正选择，并且具有雌性特异性表达，表明可能具有与性别相关的功能。此外，针尾部物种表现出许多由谱系特异性复制产生的假基因。我们得出结论，系统发育重建和假基因筛选提供了新的证据，支持膜翅目中多个tra旁系同源物是独立复制而非起源于祖先的假设。与之前认为衍生的tra旁系同源物作为CSD位点发挥作用的假设相反，榕小蜂的情况是具有复制tra的非CSD物种的第一个例子。
