Geuverink E, Beukeboom L W
Evolutionary Genetics, Center for Ecological and Evolutionary Studies, University of Groningen, Groningen, The Netherlands.
Sex Dev. 2014;8(1-3):38-49. doi: 10.1159/000357056. Epub 2013 Dec 21.
Sex determination in insects is characterized by a gene cascade that is conserved at the bottom but contains diverse primary signals at the top. The bottom master switch gene doublesex is found in all insects. Its upstream regulator transformer is present in the orders Hymenoptera, Coleoptera and Diptera, but has thus far not been found in Lepidoptera and in the basal lineages of Diptera. transformer is presumed to be ancestral to the holometabolous insects based on its shared domains and conserved features of autoregulation and sex-specific splicing. We interpret that its absence in basal lineages of Diptera and its order-specific conserved domains indicate multiple independent losses or recruitments into the sex determination cascade. Duplications of transformer are found in derived families within the Hymenoptera, characterized by their complementary sex determination mechanism. As duplications are not found in any other insect order, they appear linked to the haplodiploid reproduction of the Hymenoptera. Further phylogenetic analyses combined with functional studies are needed to understand the evolutionary history of the transformer gene among insects.
昆虫的性别决定以一种基因级联为特征，这种基因级联在底部是保守的，但在顶部包含多种初级信号。所有昆虫中都存在底部的主控开关基因双性基因（doublesex）。其上游调节因子transformer存在于膜翅目、鞘翅目和双翅目中，但迄今为止在鳞翅目和双翅目的基部类群中尚未发现。基于其共享结构域以及自我调节和性别特异性剪接的保守特征，transformer被推测为全变态昆虫的祖先基因。我们认为，它在双翅目基部类群中的缺失以及其特定目保守结构域表明它在性别决定级联中经历了多次独立的丢失或招募。在膜翅目的衍生科中发现了transformer的重复，这些科以其互补性别决定机制为特征。由于在任何其他昆虫目中都未发现重复现象，它们似乎与膜翅目的单倍体二倍体繁殖有关。需要进一步的系统发育分析结合功能研究来了解昆虫中transformer基因的进化历史。
