Gene duplication of green (RH2) opsin genes and their spectral differentiation is well documented in many teleost fish. However, their evolutionary divergence or conservation patterns among phylogenetically close but ecologically diverse species is not well explored. Medaka fish (genus Oryzias) are broadly distributed in fresh and brackish waters of Asia, with many species being laboratory-housed and feasible for genetic studies. We previously showed that a Japan strain (HNI) of medaka (O. latipes) possessed three RH2 opsin genes (RH2-A, RH2-B and RH2-C) encoding spectrally divergent photopigments. Here we examined the three RH2 opsin genes from six Oryzias species representing three species groups: the latipes, the celebensis and the javanicus. Photopigment reconstitution revealed that the peak absorption spectra (λ_max) of RH2-A were divergent among the species (447∼469 nm) while those of RH2-B and RH2-C were conservative (516∼519 nm and 486∼493 nm, respectively). For the RH2-A opsins the largest spectral shift was detected in the phylogenetic branch leading to the latipes group. A single amino-acid replacement T94C explained most of the spectral shift. For RH2-B and -C opsins we detected tracts of gene conversion between the two genes homogenizing them. Nevertheless, several amino acid differences were maintained. We showed that the spectral difference between the two opsins was attributed to largely the E/Q amino acid difference at the site 122 and to several sites with individually small spectral effects. These results depict dynamism of spectral divergence of orthologous and paralogous green opsin genes in phylogenetically close but ecologically diverse species exemplified by medaka.

中文翻译：

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Oryzias属Medaka鱼中一式三份的绿色视蛋白基因的分子进化中的直系同源分化和旁系抗融合。

在许多硬骨鱼中，绿色（RH2）视蛋白基因的基因复制及其光谱分化已得到充分证明。但是，它们在系统发育上接近但生态上不同的物种之间的进化差异或保守模式尚未得到很好的探索。Medaka鱼（Oryzias属）广泛分布在亚洲的淡咸水域，许多物种是实验室饲养的，并且对于遗传研究是可行的。我们以前表明，日本高of（O. latipes）株（HNI）具有三个RH2视蛋白基因（RH2-A，RH2-B和RH2-C），它们编码光谱上不同的色素。在这里，我们检查了来自六个Oryzias的三个RH2 opsin基因代表三个物种组的物种：Latipes，celebensis和Javanicus。光色素的重构显示，RH2-A的峰值吸收光谱（_λmax）在物种（447〜469 nm）之间发散，而RH2-B和RH2-C的吸收光谱较为保守（516〜519 nm和486〜493 nm，分别）。对于RH2-A视蛋白，在系统发育分支中检测到最大光谱位移，导致latipes组。单个氨基酸替代品T94C解释了大部分光谱偏移。对于RH2-B和-C视蛋白，我们检测到使它们均化的两个基因之间的基因转换过程。尽管如此，仍保持了几种氨基酸差异。我们表明，两种视蛋白之间的光谱差异主要归因于位点122的E / Q氨基酸差异，以及归因于个别光谱效应小的几个位点。这些结果描述了在系统发育上接近但生态多样的物种中以直为代表的直系同源和旁系绿色视蛋白基因的光谱差异的动态性。