Abstract：
Among tetrapod (terrestrial) vertebrates, amphibians remain more closely tied to an amphibious lifestyle than amniotes, and their visual opsin genes may be adapted to this lifestyle. Previous studies have discussed physiological, morphological, and molecular changes in the evolution of amphibian vision. We predicted the locations of the visual opsin genes, their neighboring genes, and the tuning sites of the visual opsins, in 39 amphibian genomes. We found that all of the examined genomes lacked the Rh2 gene. The caecilian genomes have further lost the SWS1 and SWS2 genes; only the Rh1 and LWS genes were retained. The loss of the SWS1 and SWS2 genes in caecilians may be correlated with their cryptic lifestyles. The opsin gene syntenies were predicted to be highly similar to those of other bony vertebrates. Moreover, dual syntenies were identified in allotetraploid Xenopus laevis and X. borealis. Tuning site analysis showed that only some Caudata species might have UV vision. In addition, the S164A that occurred several times in LWS evolution might either functionally compensate for the Rh2 gene loss or fine-tuning visual adaptation. Our study provides the first genomic evidence for a caecilian LWS gene and a genomic viewpoint of visual opsin genes by reviewing the gains and losses of visual opsin genes, the rearrangement of syntenies, and the alteration of spectral tuning in the course of amphibians\' evolution.
摘要：
在四足动物（陆生）脊椎动物中，两栖动物与两栖动物的生活方式比羊膜动物更紧密地联系在一起，他们的视觉视蛋白基因可能会适应这种生活方式。以前的研究已经讨论过生理，形态学,两栖动物视觉进化中的分子变化。我们预测了视觉视蛋白基因的位置，它们的邻近基因，和视觉视蛋白的调谐位置，在39个两栖动物基因组中。我们发现所有检查的基因组都缺乏Rh2基因。盲肠基因组进一步丢失了SWS1和SWS2基因；仅保留了Rh1和LWS基因。盲肠中SWS1和SWS2基因的丢失可能与其隐秘的生活方式有关。预计视蛋白基因同系物与其他骨脊椎动物的同系物高度相似。此外，在同种四倍体非洲爪狼和X中鉴定出双重同系物。调整站点分析表明，只有某些Caudata物种可能具有紫外线视觉。此外,在LWS进化中多次出现的S164A可能在功能上补偿Rh2基因丢失或微调视觉适应。我们的研究通过回顾视觉视蛋白基因的得失，为盲肠LWS基因和视觉视蛋白基因的基因组观点提供了第一个基因组证据。合时点的重新排列，以及两栖动物演化过程中光谱调谐的改变。
