Study on a resistibility mechanism - Mehler reaction - of photosynthesis against light stress in conifer

2023 Fiscal Year Final Research Report

• Project/Area Number: 19K06148
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 40010:Forest science-related
• Research Institution: Kyushu University
• Principal Investigator: Tsuyama Michito 九州大学, 農学研究院, 助教 (10380552)
• Project Period (FY): 2019-04-01 – 2024-03-31
• Keywords: 裸子植物 / 針葉樹 / 光合成 / 環境ストレス耐性

Outline of Final Research Achievements

The Mehler reaction, which is an oxygen reduction reaction at the downstream of photosystem I (PSI), has been attracted much attention for so long as an important factor relating to tolerance to high light of plants. In general, gymnosperms have a higher (about 10 times) capacity of the Mehler reaction than angiosperms. In assaying a regulation of the Mehler reaction, the presence of the cyclic electron transport around PSI, which returns electrons from acceptor side of PSI to the plastoquinone pool, becomes problem. The two reactions compete for electrons and are difficult to be measured separately. In this study, methods to detect and analyze the activity of the PSI cyclic electron flow has been established by measuring the prompt and delayed chlorophyll fluorescence. Also, it was found that analyses of redox state of P700, the reaction center of PSI, provides a basis of estimating the quantum yield of the PSI cyclic electron flow.

Free Research Field

樹木生理学

Academic Significance and Societal Importance of the Research Achievements

メーラー反応と系Ⅰサイクリック電子伝達反応は共に1950年代に発見された。植物の光ストレス耐性との関連でいずれにも数多くの研究がある。しかし、先行研究の多くは草本植物（各種主要作物、近年ではモデル植物）においてであり、裸子植物や針葉樹での例は皆無であった。草本植物における研究においてメーラー反応は無視しうる程小さいとされ、且つ、系Ⅰサイクリックも生理学的条件下では機能しないとの認識が最近まで主流であった。本研究の成果によって今後、裸子植物（針葉樹）の光ストレス耐性の仕組みや制御に関する研究が進むと期待される。草本植物における両反応の意義を再び検証する契機ともなりうる。