Molecular cloning and characterization of a cDNA for an iron-superoxide dismutase in rice (Oryza sativa L.)

We have isolated a cDNA encoding Fe-SOD from rice (Oryza sativa L.). The deduced amino acid sequence consists of a polypeptide with 255 amino acids, including a putative transit peptide (40 a.a.) in amino-terminal residues. This sequence is similar to the known plant Fe-SODs but not classified in the group of known Fe-SODs. The metal analysis and SOD assays of the partial purified recombinant protein expressed in E. coli showed that this cDNA encodes an iron-containing SOD. However this SOD activity was not inhibited by the treatment with hydrogen peroxide, which was expected to inhibit known Fe-SOD activity. mRNA of rice Fe-SOD was detected in all vegetative tissues examined, being especially abundant in calli, and strongly increased by light induction. These results suggested that this cDNA encodes rice Fe-SOD, which is apparently distinct from known plant Fe-SODs.