Phytochrome-mediated control of respiratory activities of mitochondria in cotyledons of dark-grown cucumber seedlings |
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Authors: | Yukio Morohashi Shin-ichirou Sasanuma Tadahito Seto |
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Institution: | Faculty of Agriculture, Tokyo Univ. of Agriculture and Technology, Fuchu, Tokyo 183, Japan. |
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Abstract: | Mitochondria isolated from cotyledons of dark-grown cucumber ( Cucumber sativus L., cv. Shimotsuki-Aonaga) seedlings after illumination with continuous far-red light showed an increased capacity for oxidation of malate or α-ketoglutarate, as compared with those from cotyledons of non-illuminated seedlings. This increase is supposed to be caused by phytochrome action (high irradiance response). Exogenous NAD+ had no effect on the rate of the oxidation of α-ketoglutarate or malate by mitochondria isolated from far-red light-treated cotyledons, but it enhanced the oxidation rate of mitochondria from control cotyledons to the level of mitochondria from light-treated ones. The NAD (NAD++ NADH) content was higher in mitochondria isolated from continuously far-red light-treated cotyledons than in mitochondria from controls. The NAD content was also increased by the treatment with a red light pulse and this response was reversed by a subsequent far-red light pulse. It is proposed that phytochrome controls respiratory activities of cucumber mitochondria by changing the size of the NAD pool in the mitochondria. |
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Keywords: | Cucumber Cucumis sativus mitochondria NAD pool phytochrome respiration |
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