Poster: Oxidative Stress
Abs #
114: Exon-intron structure of the chloroplastic CuZn-SOD genes in eukaryotic alga and land plants: its implication in the molecular evolution.
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Presenter: |
Kanematsu, Sumio , kanemats@nankyudai.ac.jp | Authors | Kanematsu, Sumio (A) Fujita, Kenichi (A) Ueno, Shinpei (A) Asada, Kozi (B) | | Affiliations: |
(A): Dept. Food Science and Technology, Minami-Kyushu University, Miyazaki 884-0003, Japan
(B): Dept. Biotechnology, Fac. Life Science and Biotechnology, Fukuyama University, Fukuyama 729-0292, Japan
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CuZn-superoxide dismutase(SOD) locates on thylakoid membranes and prevent oxidative stress by participating in water-water cycle in chloroplasts. Although most eukaryotic algae lack CuZn-SOD, some groups linking to land plants contain this isozyme. Therefore, it is interesting to investigate the molecular evolution of CuZn-SOD in plants. We have previously cloned cDNAs encoding chloroplastic(Chl) CuZn-SOD from the eukaryotic alga Spirogyra sp.(DDBJ, AB075698), the moss Pogonatum inflexum (AB079114, AB079115), the fern Equisetum arvense(AB079540) and maize (sod-1, AB078737), and cDNAs for cytosolic(Cyt) CuZn-SOD from the moss(AB079116) and the fern(AB079541). Their amino acid sequences suggest that the Spirogyra enzyme is a branching point of Chl and Cyt CuZn-SOD isozymes in plants. Here, we have isolated the complete genomic genes for Chl CuZn-SOD from Spirogyra and maize, and the partial gene from P. inflexum. The algal gene sequenced for 3,402 bp contains nine exons and eight introns while higher plant Chl CuZn-SOD genes so far reported eight and seven, respectively. Maize Chl CuZn-SOD gene confirmed the higher plant gene structure. The exon-intron structure of the Spirogyra gene was the same as those of the plant Chl genes except for the first intron. The first intron (191 bp) locates at 9 bp upstream from the cleavage site of Chl transit peptide, which is identical site of the first intron in 5'-UTR of the plant Cyt genes. The Chl gene of P. inflexum lacks the corresponding intron in the transit peptide region, which is resemble to those of higher plants, but contains a additional long intron (1.8 kb) in 5'-UTR, which is unique among plant Chl genes. Thus, the Spirogyra gene seems to represent an ancestor for both Chl and Cyt CuZn-SOD isozymes.
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