1985 Fiscal Year Final Research Report Summary
Study of <C_4> Photosynthesis as a Model of Intercellular Differentiation of Organelles in the Assimilatory Tissue of Higher Plants
| Project/Area Number |
59440014
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| Research Category |
Grant-in-Aid for General Scientific Research (A)
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| Allocation Type | Single-year Grants |
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| Research Field |
林産学
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| Research Institution | Kyoto University |
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Principal Investigator |
KANAI Ryuzi 京都大学, 農, 教授 (30026497)
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| Project Period (FY) |
1984 – 1985
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| Keywords | C4 plant / chloroplast / permeability of envelope / pyruvate / glycerate / photosystem 1 / chlorophyll protein complex |
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| Research Abstract |
Plant leaf tissues are differentiated and coordinated for the photosynthetic function. We investigate the functional differentiation of organelles in mesophyll cells(M) and bundle sheath cells(B) of <C_4> plants by comparing them with those of <C_3> plant leaves. Intact organelles (chloroplasts, mitochondria and peroxisomes) were isolated from the protoplasts of each cell type by differential and sucrose density gradient centrifugation.
1. M-mitochondria of various <C_4> plants lacked enzymes of photorespiratory glycolate pathway, while B-mitochondria possessed these enzymes. In contrast, M- and B-peroxisomes of Panicum miliaceum were similar to those of <C_3> plant leaves except lower activities of the enzymes in the former.
2. M- and B-chloroplasts of P. miliaceum were investigated for the uptake of metabolites. <^(14)C> -pyruvate was incorporated into both chloroplasts. In the light, the initial rate and final level of the uptake by M-chloroplasts were more than ten times of those in
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darkness. Formation of the capacity of pyruvate uptake by the illumination followed similar kinetics of pH and ATP changes in the stroma. Light dependent <^(14)C> -glycerate uptake were seen in both type of <C_4> chloroplasts.
3. Phtosynthetic and photorespiratory enzyme activities of green leaves were compared with those of colorless parts of variegated leaves of Stenotaphrum secundatum. In the colorless tissue, chloroplastic and cytoplasmic enzymes of <C_4> photosynthesis as well as mitochondrial and peroxisomal enzymes of glycolate pathway were coordinatedly reduced in their activity.
4. A pigment protein complex of photosystem 1 with 4 subunits was isolated from spinach chloroplasts. The 66kD subunit had P700 and an ironsulfur center(X). Contents of an epimer of chlorophyll a (chl a') in a variety of preparations were found to be close to 2 on the P700 basis, indicating that P700 is a dimer of chl a'. Reconstitution experiment using a P700-free 66kD apoprotein also supported this hypothesis. Less
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