カエルの視覚を超えた光センサータンパク質の意外な多様性(Unexpected diversity of light-sensing proteins goes beyond vision in frogs)

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2024-06-17 ペンシルベニア州立大学(PennState)

ペンシルバニア州立大学の研究によると、カエルは進化の過程で多様な光感受性タンパク質(オプシン)を保持してきました。オプシンは視覚だけでなく、概日リズムの調整やメラトニンの放出など、多くの生物学的機能に関与しています。研究チームは、81種のカエルの遺伝データを解析し、現代のカエルの多くが18種類の非視覚オプシンを保持していることを発見しました。これは、カエルが異なる環境での生活史を持つためと考えられています。この研究は非視覚オプシンの進化とその機能に関する重要な知見を提供し、将来の研究に寄与することが期待されています。

<関連情報>

カエルの非視覚オプシン遺伝子の環境・発生・形態適応における多様性と分子進化 Diversity and Molecular Evolution of Nonvisual Opsin Genes across Environmental, Developmental, and Morphological Adaptations in Frogs

John L Boyette, Rayna C Bell, Matthew K Fujita, Kate N Thomas, Jeffrey W Streicher, David J Gower, Ryan K Schott
Molecular Biology and Evolution  Published:13 May 2024
DOI:https://doi.org/10.1093/molbev/msae090

カエルの視覚を超えた光センサータンパク質の意外な多様性(Unexpected diversity of light-sensing proteins goes beyond vision in frogs)

Abstract

Nonvisual opsins are transmembrane proteins expressed in the eyes and other tissues of many animals. When paired with a light-sensitive chromophore, nonvisual opsins form photopigments involved in various nonvisual, light-detection functions including circadian rhythm regulation, light-seeking behaviors, and seasonal responses. Here, we investigate the molecular evolution of nonvisual opsin genes in anuran amphibians (frogs and toads). We test several evolutionary hypotheses including the predicted loss of nonvisual opsins due to nocturnal ancestry and potential functional differences in nonvisual opsins resulting from environmental light variation across diverse anuran ecologies. Using whole-eye transcriptomes of 81 species, combined with genomes, multitissue transcriptomes, and independently annotated genes from an additional 21 species, we identify which nonvisual opsins are present in anuran genomes and those that are also expressed in the eyes, compare selective constraint among genes, and test for potential adaptive evolution by comparing selection between discrete ecological classes. At the genomic level, we recovered all 18 ancestral vertebrate nonvisual opsins, indicating that anurans demonstrate the lowest documented amount of opsin gene loss among ancestrally nocturnal tetrapods. We consistently found expression of 14 nonvisual opsins in anuran eyes and detected positive selection in a subset of these genes. We also found shifts in selective constraint acting on nonvisual opsins in frogs with differing activity periods, habitats, distributions, life histories, and pupil shapes, which may reflect functional adaptation. Although many nonvisual opsins remain poorly understood, these findings provide insight into the diversity and evolution of these genes across anurans, filling an important gap in our understanding of vertebrate opsins and setting the stage for future research on their functional evolution across taxa.

生物化学工学
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