Department of Biology, Wilfrid Laurier University, Waterloo, Canada; University of Tehran, Tehran, Iran.
Department of Biology, Wilfrid Laurier University, Waterloo, Canada.
Comp Biochem Physiol A Mol Integr Physiol. 2022 Dec;274:111300. doi: 10.1016/j.cbpa.2022.111300. Epub 2022 Aug 27.
Stomach loss has occurred independently multiple times during gnathostome evolution with notable frequency within the Teleostei. Significantly, this loss of acid-peptic digestion has been found to correlate with the secondary genomic loss of the gastric proton pump subunits (atp4a, atp4b) and pepsinogens/pepsins (pga, pgc). Gastric glands produce gastric juice containing the acid and pepsin and thus their presence is a hallmark feature of a digestive system capable of acid-peptic digestion. However, in gobiid fishes although oesogaster and gastric glands have been identified histologically, their functional significance has been questioned. In the present study we address whether the gastric proton pump is present and expressed in gastric glands of the goby Neogobius species (Gobiidae) and in members of the family Oxudercidae, a group of amphibious gobiid fishes commonly known as mudskippers (genera: Periophthalmus, Boleophthalmus, Periophthalmodon and Scartelaos). We confirmed the presence of gastric glands and have immunohistochemically localized gastric proton pump expression to these glands in Neogobius fluviatilis and Periophthalmus novemradiatus, Periophthalmus barbarus and Boleophthalmus boddarti. Genome analysis in Neogobius melanostomus, Periophthalmus magnuspinnatus, Scartelaos histophorus, Boleophthalmus pectinirostris, and Periophthalmodon schlosseri revealed the presence of both atp4a and atp4b subunit orthologues in all species in a conserved genomic loci organization. Moreover, it was possible to deduce that the complete open reading frame and the key functional amino acid residues are present. The conserved expression of the gastric proton pump provides clear evidence of the potential for gastric acid secretion indicating that acid digestion is retained in these gobiid fishes and not lost.
胃的丧失在颌口动物的进化中多次独立发生，在硬骨鱼类中尤为频繁。值得注意的是，这种酸-肽消化的丧失与胃质子泵亚基(atp4a、atp4b)和胃蛋白酶原/胃蛋白酶(pga、pgc)的次级基因组丧失有关。胃腺分泌含有酸和胃蛋白酶的胃液，因此它们的存在是能够进行酸-肽消化的消化系统的一个显著特征。然而，在虾虎鱼中，尽管已经从组织学上鉴定出了咽胃和胃腺，但它们的功能意义一直受到质疑。在本研究中，我们探讨了胃质子泵是否存在于虾虎鱼 Neogobius 种（虾虎鱼科）和 Oxudercidae 科成员的胃腺中，Oxudercidae 科是一组通常被称为弹涂鱼的两栖虾虎鱼（属：Periophthalmus、Boleophthalmus、Periophthalmodon 和 Scartelaos）。我们证实了胃腺的存在，并通过免疫组织化学将胃质子泵的表达定位到 Neogobius fluviatilis 和 Periophthalmus novemradiatus、Periophthalmus barbarus 和 Boleophthalmus boddarti 的胃腺中。在 Neogobius melanostomus、Periophthalmus magnuspinnatus、Scartelaos histophorus、Boleophthalmus pectinirostris 和 Periophthalmodon schlosseri 中的基因组分析表明，所有物种在保守的基因组位点组织中都存在 atp4a 和 atp4b 亚基的同源物。此外，还可以推断出完整的开放阅读框和关键的功能氨基酸残基都存在。胃质子泵的保守表达提供了胃酸分泌的潜在能力的明确证据，表明这些虾虎鱼保留了酸消化，而没有丧失。
