2001 Fiscal Year Final Research Report Summary
Molecular basis for decline of leaf function during senescence: Analysis of major determinants causing decline of the amount of Rubisco
| Project/Area Number |
12460028
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Plant nutrition/Soil science
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| Research Institution | Tohoku University |
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Principal Investigator |
MAE Tadahiko Graduate School of Agricultural Science, Tohoku University, Professor, 大学院・農学研究科, 教授 (60134029)
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| Co-Investigator(Kenkyū-buntansha) |
ISHIDA Hiroyuki Graduate School of Agricultural Science, Tohoku University, Assistant Professor, 大学院・農学研究科, 助手 (60312625)
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| Project Period (FY) |
2000 – 2001
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| Keywords | rbcS / rbcL / Rubisco / Turnover / Senescence / Rice |
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| Research Abstract |
1) Rubisco was actively synthesized during expansion, but the amount of Rubisco synthesized rapidly declined just before full expansion. It already declined to about one fifth of the maximal amount at the time of fall expansion, and further declined to about one-tenth during senescence. The changes in the levels of rbcL and rbcS mRNAs were almost coordinated with those changes in the amount of Rubisco synthesized. Thus, the amount of Rubisco synthesized was primarily determined by the levels of rbcL and rbcS mRNAs throughout the life span of the leaves. Degradation of Rubisco became far more active than synthesis of Rubisco during senescence. Since the synthesis of Rubisco during senescence scarcely contributed to its amount, the degradation of Rubisco is the major determinant for the amount of Rubisco in the senescent leaves.
2) The large subunit of Rubisco (LSU) was directly fragmented at Gly-329 into the 37-kDa and 16-kDa fragments by reactive oxygen species generated in the illuminated lysates of chloroplasts or intact chloroplasts. The LSU could also be cleaved into several other fragments by increasing the incubation time or the Fe^<2+> concentrations. All the cleavage sites were at or very close to the active site, just around the metal binding site within a radius of 12Å, indicating that proximity and favorable orientation are probably the most important parameter determining the cleavage sites. GS2 was also degraded by reactive oxygen species with the same manner as the LSU.
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