The maize mitochondrial mnsods encoded by multiple genes are localized in the mitochondrial matrix of transformed yeast cells

We recently demonstrated that maize mitochondrial MnSODs are encoded by a differentially expressed multigene family. Molecular characterization of the cloned maize MnSod cDNAs shows that all the maize MnSODs encoded by the cloned MnSod have mitochondrial transit peptides and that the matrix-targeting signal was conserved in all the MnSOD precursor proteins, suggesting that all the maize MnSODs are associated with mitochondria in vivo. In an attempt to clarify the submitochondrial localization of each individual maize MnSOD, each of the maize MnSod cDNAs was introduced into the MnSOD-deficient yeast cells. The functional role and submitochondrial location of each individual MnSOD were examined in the transformed yeast cells. Herein, we demonstrate that all the maize MnSODs can functionally complement the MnSOD deficiency and rescue the transformed yeast cells from oxidative stress induced by paraquat. Biochemical analyses indicate that all of the maize MnSODs are expressed and targeted into the mitochondrial matrix of transformed yeast cells.