2007 Fiscal Year Final Research Report Summary
Study for the endosymbiosis and cross-talk by the search and analysis of duplicated genes both nucleus and organelle genome.
| Project/Area Number |
17570187
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Evolutionary biology
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| Research Institution | Saitama University |
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Principal Investigator |
OHTA Niji Saitama University, Graduate school of science and engeneering, Lecturer (60257186)
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| Project Period (FY) |
2005 – 2007
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| Keywords | nucleus / chloroplast / cbbX / secA / endosymbiosis / RuBisCO |
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| Research Abstract |
Mitochondria and chloroplasts have their own genomes, but many of the genes those used in the organella are encoded in the cell nucleus. It is not unclear how the cell nucleus communicate organelles.
Genome sequence of Cyanidioschyzon merolae, a unicellular red alga, was completed and I found that two kind of genes are encoded one is in the cell nulcleus and the other in the plastid genome. One gene is cbbX, a gene that is concerned to the gene expression of RuBisCO. The cbbX gene is generally encoded in proteobacterial genomes and red-algal plastid genomes. The phylogenetic tree inferred from cbbX genes and strongly conserved gene organization (rbcLS-cbbX) suggests that the plastid-encoded cbbX gene of C. merolae came from an ancestral proteobacterium by horizontal gene transfer. On the other hand, the nuclear-encoded cbbX was classified in another cluster together with the nucleomolph-encoded cbbX gene of Guillardia theta. Furthermore, expression of the two cbbX genes were regulated differently in response to extracellular CO2 concentration. The results imply that cbbX gene in the plastid genome was copied and transferred to the cell nucleus after horizontal gene transfer of RuBisCO operon from ancestral beta-proteobacteria at comparatively early stage, and that each cbbX evolved in different ways.
Another gene that are encoded both in the cell nucleus and the plastid genome is secA which is included the sec pathway in chloroplasts and bacteria. Molecular phylogenetic analysis showed that secA encoded in the cell nucleus and in the chloroplast genome are not the same origin.
The two secAs were cloned and expressed in Escherichia coli. Overexpression of secA in the chloroplast genome repressed the growth of E. coli though that of in the cell nucleus did not. The result suggested that the two secA genes work different ways in the chloroplast.
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