Molecular backgrounds for the seawater adaptation in euryhaline medaka (Oryzias latipes).

2020 Fiscal Year Final Research Report

• Project/Area Number: 18K14740
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 44040:Morphology and anatomical structure-related
• Research Institution: The University of Tokyo
• Principal Investigator: Takagi Wataru 東京大学, 大気海洋研究所, 助教 (90755307)
• Project Period (FY): 2018-04-01 – 2021-03-31
• Keywords: エピジェネティクス / 進化 / 海水適応 / RNA-seq / ATAC-seq

Outline of Final Research Achievements

Medaka is an ideal model to study seawater adaptation of teleost fishes. In this study, the following four experimental groups were prepared: Group1, reared in seawater; Group2, transferred back to freshwater; Group3 and Group4, freshwater group control for Group1 and Group2, respectively (reared at the same condition except for salinity). The gills of each group were then analyzed by RNA-seq and ATAC-seq. At the transcriptome level, the expression profiles of Group1 and Group2 were clearly different, while the profile of Group3 strongly resembled that of Group4. Meanwhile, ATAC-seq analysis showed that the profile of the differentially accessible (DA) peaks in seawater-experienced Group2 is likely intermediate states between those of Group1 and Group3. These findings suggest that the seawater experience in medaka may be memorized at the chromatin level but not at the transcriptome level.

Free Research Field

魚類生理学

Academic Significance and Societal Importance of the Research Achievements

国産の小型魚類メダカは、海水への適応能力が高く、海水適応機構の研究に最適なモデル生物である。本研究では、海水へ移行させた個体が淡水へと戻った後も、海水中のクロマチン状態を一定レベル保持することで、淡水で飼育を続けた個体と比べて海水適応能力を向上させる可能性が示唆された。このクロマチン状態の記憶は、高い頻度で起こる環境変化に対して有利にはたらくと考えられ、適応進化を理解する上で重要な基礎的知見である。また、最近の研究では、一度海水を経験した魚が、淡水で飼育され続けた個体と比べて、成長がよくなることが報告されており、水産増養殖への応用も期待される。