Abstract
The green alga Spirogyra contained two types of Mn-SOD genes similar to the mitochondrial genes of land plants and of the green alga Chlamydomonas, respectively. To investigate the evolutional relationship between the two Mn-SOD, we have analyzed their genomic genes and characterized their products. The algal-type of Mn-SOD gene consisted of 6 exons and the positions of 5 introns differed from those of the land plant-type gene, indicating that their exon-intron structure was different. To the contrary, the positions of 5 introns of the land plant-type Mn-SOD gene were identical with those of two Mn-SOD genes of Arabidopsis. Recombinant proteins of both types of Mn-SOD indicated that the algal-type of Mn-SOD was a homodimer while the land plant-type was a homotetramer. Thus, the above data suggested that the algal-type and land plant-type of Mn-SODs were diverged at the early phase of the molecular evolution of the Mn-SOD.
