| Photosynthesis in plants converts light energy from the sun to energy available for all living things on the earth. Effective utilization of this process can potentially reduce environmental problems, such as shortage of fossil fuels, and increased CO2 levels in the atmosphere. The protein complexes responsible for photosynthesis are easily affected by changes in the external environment, resulting in a suppression of a reaction and finally in a reduction of the growth of the whole plant. To retain the optimum yield of photosynthesis, plants respond to changes in their environment by regulating and stabilizing photosynthetic machinery. Thus, understanding the mechanisms of stress response is a key factor in ensuring the effective utilization of photosynthetic performance. In this division, we are studying molecular mechanisms of response to stress in plants and cyanobacteria (known as the origin of chloroplasts in higher plants). Particular focuses are made on revealing the mechanisms of stabilization and reactivation of photosynthetic machinery. By using the knowledge obtained from these researches, we are also attempting gene manipulation of plants to enhance their tolerance to environmental stress, for example, salt stress and high-temperature stress (Fig A). |
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| The mechanisms that stabilize the photosynthetic activity under high-temperature conditions are studied. One of the goals is to enhance their tolerance to high temperature by gene manipulation. |
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| We have altered the molecular structure of the metal-binding proteins that detoxify or reserve heavy metals to increase the ability of metal binding. The final goal of this approach will be the utilization of plants to remove toxic metal ions from soil contaminated with heavy metals. |
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| Metabolism of nucleic acid derivatives is important to avoid toxicity and to reuse nitrogen resources. We are characterizing ADP-ribose pyrophosphatases that regulate the levels of nitrogen compounds in response to environmental stress. |
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| To understand protective mechanisms against oxidative stress in plants and cyanobacteria, we are studying the effects of oxidative stress on the translational machinery which is important for the repair of photosynthesis. |
| Figure B. Predicted 3D-structure of the dimeric form of cyanobacterial ADP-ribose pyrophosphatase. Functionally important glutamic acid residues are indicated. |
| Figure A. Growth of wild-type (right) and transformed (left) Arabidopsis on the medium containing NaCl. Introduction of the gene for choline oxidase into Arabidopsis enhanced tolerance to salt stress with an increased level of glycinebetain (one of the typical compatible solutes). |
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