GENES ENCODING SUBUNIT-6 OF NADH DEHYDROGENASE AND SUBUNIT-6 OF ATP SYNTHASE ARE CO-TRANSCRIBED IN MAIZE MITOCHONDRIA

The mitochondrial nad6 gene of maize was identified and mapped 1 kb do wnstream from the atp6 gene. It encodes a 220 amino-acid polypeptide. Using Northern hybridization experiments and RT-PCR analysis, we showe d that both nad6 and atp6 are cotranscribed in maize mitochondria. RNA editing of the mitochondrial nad6 transcript was studied by cDNA sequ encing. Twelve edited sites were identified at the same positions as t hose already identified in the wheat mitochondria nad6 transcript. Ali gnments of nucleotide and amino-acid sequences of the mitochondrial na d6 genes of maize, wheat, and Brassica campestris, show that the wheat gene encodes a shorter polypeptide (229 amino acids) than was previou sly thought.