Developmental analysis of steady-state levels of Cu/Zn and Mn superoxide dismutase mRNAs in maize [Zea mays] tissues

The superoxide dismutase (Sod) steady-state mRNA levels in maize seedlings and developing kernels were examined by RNA blot analysis, using Cu/Zn and Mn cDNA probes encoding the cytosolic and mitochondrial SOD isozymes, respectively. The cytosolic (Cu/Zn) Sod steady-state mRNA levels remained relatively constant for the various tissues examined. In contrast, the mRNA levels of the mitochondrial (Mn) SOD-3 isozyme increased in postgerminative scutella. The steady-state mRNA of the Atp2 gene, F1 ATPase β subunit, was compared to the Sod3 (Mn) mRNA levels. Results of this comparative study suggest that the steady-state levels of mRNAs transcribed by nuclear genes encoding essential mitochondrial proteins are independently regulated throughout development.