Skelly J, Pushparajan C, Duncan E J, Dearden P K
Laboratory for Evolution and Development, Genomics Aotearoa, Biochemistry Department, University of Otago, Dunedin, Aotearoa-New Zealand.
School of Biology, Faculty of Biological Sciences, University of Leeds, Leeds, UK.
Insect Mol Biol. 2019 Jun;28(3):392-408. doi: 10.1111/imb.12560. Epub 2019 Jan 24.
Embryonic terminal patterning and moulting are critical developmental processes in insects. In Drosophila and Tribolium both of these processes are regulated by the Torso-activation cassette (TAC). The TAC consists of a common receptor, Torso, ligands Trunk and prothoracicotropic hormone (PTTH), and the spatially restricted protein Torso-like, with combinations of these elements acting mechanistically to activate the receptor in different developmental contexts. In order to trace the evolutionary history of the TAC we determined the presence or absence of TAC components in the genomes of arthropods. Our analyses reveal that Torso, Trunk and PTTH are evolutionarily labile components of the TAC with multiple individual or combined losses occurring in the arthropod lineages leading to and within the insects. These losses are often correlated, with both ligands and receptor missing from the genome of the same species. We determine that the PTTH gene evolved in the common ancestor of Hemiptera and Holometabola, and is missing from the genomes of a number of species with experimentally demonstrated PTTH activity, implying another molecule may be involved in ecdysis in these species. In contrast, the torso-like gene is a common component of pancrustacean genomes.
胚胎末端模式形成和蜕皮是昆虫重要的发育过程。在果蝇和赤拟谷盗中，这两个过程均由躯干激活盒（TAC）调控。TAC由一个共同的受体躯干、配体Trunk和促前胸腺激素（PTTH）以及空间受限的蛋白类躯干组成，这些元件的组合在不同发育环境中通过机械作用激活受体。为了追溯TAC的进化历史，我们确定了节肢动物基因组中TAC组分的有无。我们的分析表明，躯干、Trunk和PTTH是TAC中进化不稳定的组分，在通向昆虫以及昆虫内部的节肢动物谱系中发生了多次单个或组合丢失。这些丢失往往相互关联，同一物种的基因组中配体和受体均缺失。我们确定PTTH基因在半翅目和全变态昆虫的共同祖先中进化而来，并且在一些具有实验证明的PTTH活性的物种基因组中缺失，这意味着可能有另一种分子参与了这些物种的蜕皮过程。相比之下，类躯干基因是泛甲壳动物基因组的常见组分。
