International Research Center for Marine Biosciences, Ministry of Science and Technology, Shanghai Ocean University, Shanghai, China.
Key Laboratory of Exploration and Utilization of Aquatic Genetic Resources, Ministry of Education, Shanghai Ocean University, Shanghai, China.
Sci Rep. 2021 Sep 29;11(1):19288. doi: 10.1038/s41598-021-98930-9.
Larval metamorphosis in bivalves is a key event for the larva-to-juvenile transformation. Previously we have identified a thyroid hormone receptor (TR) gene that is crucial for larvae to acquire "competence" for the metamorphic transition in the mussel Mytilus courscus (Mc). The mechanisms of thyroid signaling in bivalves are still largely unknown. In the present study, we molecularly characterized the full-length of two iodothyronine deiodinase genes (McDx and McDy). Phylogenetic analysis revealed that deiodinases of molluscs (McDy, CgDx and CgDy) and vertebrates (D2 and D3) shared a node representing an immediate common ancestor, which resembled vertebrates D1 and might suggest that McDy acquired specialized function from vertebrates D1. Anti-thyroid compounds, methimazole (MMI) and propylthiouracil (PTU), were used to investigate their effects on larval metamorphosis and juvenile development in M. coruscus. Both MMI and PTU significantly reduced larval metamorphosis in response to the metamorphosis inducer epinephrine. MMI led to shell growth retardation in a concentration-dependent manner in juveniles of M. coruscus after 4 weeks of exposure, whereas PTU had no effect on juvenile growth. It is hypothesized that exposure to MMI and PTU reduced the ability of pediveliger larvae for the metamorphic transition to respond to the inducer. The effect of MMI and PTU on larval metamorphosis and development is most likely through a hormonal signal in the mussel M. coruscus, with the implications for exploring the origins and evolution of metamorphosis.
双壳类幼虫变态是幼虫向幼体转变的关键事件。之前，我们已经鉴定出一种甲状腺激素受体（TR）基因，该基因对贻贝 Mytilus courscus（Mc）幼虫获得变态转变的“能力”至关重要。然而，甲状腺信号在双壳类动物中的机制在很大程度上仍不清楚。在本研究中，我们从分子水平上对两个碘甲状腺原氨酸脱碘酶基因（McDx 和 McDy）进行了全序列鉴定。系统发育分析显示，软体动物（McDy、CgDx 和 CgDy）和脊椎动物（D2 和 D3）的脱碘酶具有一个代表直接共同祖先的节点，这与脊椎动物 D1 相似，可能表明 McDy 从脊椎动物 D1 获得了特殊功能。抗甲状腺化合物甲巯咪唑（MMI）和丙硫氧嘧啶（PTU）被用于研究它们对贻贝 Mc 幼虫变态和幼体发育的影响。MMI 和 PTU 均显著降低了幼虫对变态诱导剂肾上腺素的变态反应。MMI 以浓度依赖性方式导致幼体贻贝 Mc 的壳生长迟缓，而 PTU 对幼体生长没有影响。研究假设，暴露于 MMI 和 PTU 降低了幼体贻贝对变态诱导剂的变态反应能力。MMI 和 PTU 对幼虫变态和发育的影响最有可能是通过贻贝 Mc 中的激素信号发生的，这对探索变态的起源和进化具有重要意义。
