Regulation of leaf photosynthesis at elevated CO2: roles of sugar-sensing and systemic regulation

2019 Fiscal Year Final Research Report

• Project/Area Number: 17H03693
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Plant molecular biology/Plant physiology
• Research Institution: The University of Tokyo
• Principal Investigator: Terashima Ichiro 東京大学, 大学院理学系研究科(理学部), 教授 (40211388)
• Project Period (FY): 2017-04-01 – 2020-03-31
• Keywords: 大気CO2濃度の増加 / 光合成ダウンレギュレーション / 葉肉シグナル / 葉肉コンダクタンス / 糖センサー / 気孔

Outline of Final Research Achievements

We found that not only non-structural carbohydrates but also structural ones accumulated when Arabidopsis and some legume plants were grown at high CO2. Cell walls thickened considerably by two to three folds and the mesophyll conductance measured by the carbon isotope discrimination method decreased with the increase in the cell wall thickness. Contrary to the widely-held view, starch accumulation per se did not decrease the mesophyll conductance.
Stomata are often though to move autonomously by the activity of stomatal guard cells. Here, we developed an experimental system in which the epidermal strips prepared from Commelina commmunis leaves placed on the mesophyll pre-treated in various ways. Stomatal opening in the epidermal strips was enhanced when the mesophyll segments were pre-treted at low CO2 and/or in the light. The leaf segment placed at high CO2 and/or in the dark produced negative signal(s). These mesophyll signal(s) enhanced stomatal responses.

Free Research Field

植物生理生態学・植物生理解剖学

Academic Significance and Societal Importance of the Research Achievements

大気CO2濃度が上昇している、CO2は光合成の基質であるにもかかわらず、CO2濃度の上昇は光合成や植物の成長はそれほど促進しない。世界の人口増に見合う、安定した食糧供給を可能にするためには、高CO2環境で高い生産性を示す好CO2作物の創出は必須である。そのためには、まず、高CO2応答の全貌を分子生理学レベルで知る必要がある。本研究では光合成のダウンレギュレーションのメカニズムのうち、葉肉コンダクタンスの低下の原因をほぼ特定した。デンプンの蓄積ではなく、細胞壁の肥厚であった。また、気孔のCO2応答における葉肉シグナルの実在を証明し、その重要性を指摘した。