Department of Evolutionary Biology, Integrative Zoology, University of Vienna, Althanstraße 14, Vienna 1090, Austria.
Department of Neurosciences and Developmental Biology, University of Vienna, Althanstraße 14, Vienna 1090, Austria.
Curr Biol. 2021 Jan 11;31(1):207-213.e4. doi: 10.1016/j.cub.2020.10.004. Epub 2020 Oct 29.
Ecdysis or molting evolved ∼535 mya in Ecdysozoa, the most diverse and species-rich animal superphylum. A cascade of ecdysis-related neuropeptides (ERNs) controls the innate behavioral programs required for cuticle shedding in some ecdysozoan lineages (e.g., arthropods) but is lacking in others (e.g., nematodes). We recently reported on the surprisingly ancient bilaterian origin of key ERNs, such as eclosion hormone (EH), crustacean cardioactive neuropeptide (CCAP), myoinhibitory peptide (MIP), bursicon alpha (Bursα), and bursicon beta (Bursβ). Thus, ERNs far predate the emergence of ecdysis, but the question as to their ancestral functions remains unresolved. Here, we compare the ERN toolkits and temporal expression profiles of six ecdysozoans (tardigrades, crustaceans, and insects), eight lophotrochozoans (planarians, annelids, and mollusks), and five deuterostomes (crinoids, sea urchins, and hemichordates). Our results show that the major, coordinated upregulation of ERNs always coincides with a transition between key life history stages, such as hatching in direct developers and metamorphosis in indirect developers. This implies that ERNs already played an ancestral role in the switch from embryonic or larval ontogeny to juvenile maturation in the last common ancestor of Nephrozoa. Consequently, the transcriptional signature of invertebrate life cycle transitions presented here was already in place in the Precambrian and was only secondarily co-opted into regulating the molting process at the dawn of Ecdysozoa.
蜕皮或脱壳大约在 5.35 亿年前的节肢动物中进化，这是最多样化和物种最丰富的动物超门。蜕皮相关神经肽 (ERNs) 的级联反应控制着某些节肢动物谱系（例如节肢动物）蜕皮所需的先天行为程序，但在其他谱系（例如线虫）中则缺乏。我们最近报道了关键 ERNs 的惊人古老的两侧起源，例如蜕皮激素 (EH)、甲壳动物心脏活性神经肽 (CCAP)、肌抑制肽 (MIP)、bursicon alpha (Bursα) 和 bursicon beta (Bursβ)。因此，ERNs 远在蜕皮出现之前就已经存在，但它们的祖先功能问题仍未解决。在这里，我们比较了六种节肢动物（缓步动物、甲壳动物和昆虫）、八种担轮动物（扁形动物、环节动物和软体动物）和五种后口动物（海百合、海胆和半索动物）的 ERN 工具包和时间表达谱。我们的结果表明，ERNs 的主要协调上调总是与关键生命史阶段之间的转变相一致，例如直接发育者的孵化和间接发育者的变态。这意味着 ERNs 已经在从胚胎或幼虫发生到幼年成熟的转变中发挥了祖先的作用，这是在 Nephrozoa 的最后共同祖先中。因此，这里呈现的无脊椎动物生命周期转变的转录特征已经存在于前寒武纪，并仅在节肢动物出现时被次要地选择用于调节蜕皮过程。
