The opsin genes of Amazonian cichlids

Vision is a critical sense for organismal survival with visual sensitivities strongly shaped by the environment. Some freshwater fishes with a Gondwanan origin are distributed in both South American rivers including the Amazon, as well as African rivers and lakes. These different habitats likely required adaptations to murky and clear environments. In this study, we compare the molecular basis of Amazonian and African cichlid fishes’ visual systems. We used next generation sequencing of genomes and retinal transcriptomes to examine three Amazonian cichlid species. Genome assemblies revealed six cone opsin classes (SWS1, SWS2B, SWS2A, RH2B, RH2A, LWS) and rod opsin (RH1). However, the functionality of these genes varies across species with different pseudogenes found in different species. Our results support evidence of an RH2A gene duplication event that is shared across both cichlid groups, but which was probably followed by gene conversion. Transcriptome analyses show that Amazonian s...视觉是生物体维系生存的核心感知能力，其视觉敏感度的演化深受环境因素的塑造。部分源自冈瓦纳大陆（Gondwana）的淡水鱼类，不仅分布于包含亚马孙河流域在内的南美洲水系，还见于非洲的河流与湖泊中。这类差异化的栖息环境很可能推动鱼类演化出适配浑浊与清澈水体的视觉系统。本研究针对亚马孙与非洲慈鲷（cichlid）的视觉系统分子基础开展比较分析。我们通过基因组与视网膜转录组的下一代测序技术，对3种亚马孙慈鲷进行了研究。基因组组装结果显示，该类群存在6类视锥视蛋白（cone opsin）：SWS1、SWS2B、SWS2A、RH2B、RH2A、LWS，以及1类视杆视蛋白（rod opsin）RH1。但不同物种的此类基因功能存在差异，不同物种中可检测到不同的假基因（pseudogene）。本研究结果证实，RH2A基因的复制事件在两类慈鲷类群中均存在，且该事件之后很可能发生了基因转变（gene conversion）。转录组分析显示，亚马孙的……