Cloning and expression of mitochondrial MnSOD from the small radish (Raphanus sativus L.)

A cDNA clone for a mitochondrial MnSOD was isolated from a cDNA library derived from seedlings of the small radish (Raphanus sativus L.). The cDNA clone, RsMnSOD, encoded a polypeptide with a predicted molecular mass of 25.4 kDa and calculated pI of 8.77. Its deduced amino acid sequence was 93% homologous with MnSOD of Arabidopsis. RNA gel blot analysis showed that RsMnSOD transcripts were most abundant in leaves, followed by roots and hypocotyls, whereas transcripts of RsFeSOD and RsCu/ZnSOD were not detected in roots. The hypocotyls of germinated seedlings turned green and finally red in response to white light. These color changes were accompanied by increases in RsMnSOD and RsCu/ZnSOD mRNA. In addition, RsMnSOD expression was strongly induced by osmotic stress, moderately induced by phytohormones such as ABA and IAA, and not induced by xenobiotics other than cercosporin.