Physiological analysis on mechanisms of the pineal wavelength discrimination involving the bistable opsin

2019 Fiscal Year Final Research Report

• Project/Area Number: 18K14751
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 44050:Animal physiological chemistry, physiology and behavioral biology-related
• Research Institution: Osaka City University
• Principal Investigator: Wada Seji 大阪市立大学, 大学院理学研究科, 特任助教 (90747320)
• Project Period (FY): 2018-04-01 – 2020-03-31
• Keywords: オプシン / opsin / 松果体 / pineal / ゼブラフィッシュ

Outline of Final Research Achievements

Lower vertebrates have photosensitive pineal organs, which discriminate UV and visible light (i.e., "color" detection). The pineal color detection has been considered to involve multiple photosensitive proteins (opsins), like the color sensing in eyes. However, in this study, it was found that the property of a pineal UV-sensitive opsin (the bistable opsin) enables the color detection with the UV-sensitive opsin alone. This mechanism, newly found in this study, was suggested to be the "ancestral mechanism" of human color vision. In addition, it was found that a mechanism involving another visible light-sensitive opsin is present as well as the UV-sensitive opsin. These two opsins are present in the same cells in the fish pineal organ. In the lamprey pineal, unlike fish, the two opsins are present in separate cells. These findings suggest the pineal color detection was diversified and optimized after the lamprey split from the ancestral vertebrate.

Free Research Field

光生物学

Academic Significance and Societal Importance of the Research Achievements

魚類などの脊椎動物は光感受性の松果体を有し、光の波長（"色"）情報を検出する。本研究では、眼と共通の起源から生じた、松果体という光受容器官に注目し、色情報処理機構について解析した。魚類から爬虫類までの多くの松果体の色情報処理は、共通の分子（光再生型オプシン）を用いながらも多様化していた。原始的脊椎動物である円口類の松果体は部分的に眼と共通の機構で色情報処理するが、魚類では異なっていた。このことは、進化の過程で、魚類があえて眼とは異なる色情報処理機構を獲得したとことを示唆する。すなわち、松果体と眼がそれぞれ光感覚を最適化してきた結果と考えられ、光生物学的、進化学的に重要な知見が得られたと言える。