Abstract
Superoxide dismutase (SOD) consists of three isozymes of CuZn-SOD, Mn-SOD and Fe-SOD. Although most algae lack CuZn-SOD, the green alga Spirogyra possesses this type of isozyme. Previously, we have reported the molecular evolution of CuZn-SOD by comparison of exon-intron structure of the genes from Spirogyra, moss and fern. Here, to characterize the remaining isozymes in Spirogyra we have cloned cDNAs of SOD isozymes.
PCR using isozyme-specific primers with cDNA libraries from Spirogyra, the moss Pogonatum, the fern Equisetum and maize confirmed isozyme-specific amplification of cDNA fragments. Two types of Mn-SOD cDNAs were cloned by RACE method. The clone of 1047 bp encoded 231 amino acid residues of mitochondrial SOD, most resembled to the moss gene. The other (917 bp) encoded Mn-SOD similar to Chlamydomonas enzyme lacking mitochondrial transit peptide. However, alignment of both SODs revealed their resemblance in signal region, indicating their mitochondrial localization.
