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Novel gene encoding a Ca2+-binding protein and under hexokinase-dependent sugar regulation
Shigeo Otsuki1, Akira Ikeda, Tomomi Sunako
1Division of Biological Sciences, Graduate School of Science, Hokkaido University, Kita-ku N10-W8, Sapporo 060-0810, Japan.
Bioscience, Biotechnology, and Biochemistry
|May 6, 2003
Summary
Researchers identified a novel calcium-binding protein, OsSUR1, in rice. Its gene expression is sugar-induced via a hexokinase pathway, independent of calcium signaling, primarily in plant internodes and early embryos.
Area of Science:
- Plant Molecular Biology
- Biochemistry
- Gene Regulation
Background:
- A previously isolated cDNA from sugar-induced rice embryo genes encoded a predicted 15-kDa protein.
- The function and regulatory mechanisms of this protein were not fully understood.
Purpose of the Study:
- To identify and characterize a novel calcium-binding protein from rice.
- To elucidate the regulatory pathway of the OsSUR1 gene expression.
Main Methods:
- cDNA microarray analysis for gene isolation.
- Recombinant protein expression in Escherichia coli.
- 45Ca2+ binding assays.
- Northern blot analysis for gene expression studies.
- Treatment with sugars, Ca2+ signaling inhibitors, calmodulin antagonists, and protein kinase/phosphatase inhibitors.
Main Results:
- The isolated cDNA encodes a novel calcium (Ca2+)-binding protein, OsSUR1 (Oryza sativa sugar-up-regulated-1).
- Recombinant OsSUR1 protein exhibited Ca2+ binding activity.
- OsSUR1 gene expression was predominantly observed in mature plant internodes and early-stage germinating embryos.
- Gene expression was induced by hexokinase-substrate sugars but not repressed by Ca2+ signaling inhibitors, calmodulin antagonists, or protein kinase/phosphatase inhibitors.
Conclusions:
- OsSUR1 is a novel Ca2+-binding protein in rice.
- OsSUR1 gene expression is stimulated by a hexokinase-dependent pathway.
- The sugar-induced OsSUR1 expression is not mediated by Ca2+ signaling pathways.