Effect of Methionine Sulfoximine on Photosynthetic Carbon Metabolism in Wheat Leaves

概要

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Methionine sulfoximine (MSO) greatly reduced the carbon dioxide exchange rate (CER) of detached wheat (Triticum aestivum L. cv Roland) leaves in 21% O_2, but only slightly reduced it in 2% O_2. A supply of 50 mM NH_4Cl had little effect on the CER irrespective of the O_2 concentration. A simultaneous addition of glutamine and MSO protected against the inhibition of photosynthesis to a considerable extent and caused the accumulation of more NH_3 than did the addition of MSO alone. Fixation of ^<14>CO_2 in wheat leaves was inhibited by MSO treatment in 22% O_2, and there was decreased incorporation of<14^>C into amino acids and sugars and increased label into acid fractions. The addition of MSO and glutamine together eliminated the effect of MSO on the photosynthetic ^<14>CO_2 fixation pattern. NH_4Cl stimulate_d the synthesis of amino acids from ^<14>CO_2, especially the synthesis of serine in 22% O_2. Our observations show that factors other than the uncoupling of photophosphorylation by accumulated NH_3 may be responsible for the early stage of photosynthesis inhibition by MSO under photorespiratory conditions.
日本植物生理学会の論文