Molecular weights of maize mitochondrial and cytoplasmic ribosomal RNAs under denaturing conditions

The molecular weights of maize cytoplasmic and mitochondrial rRNAs were determined by gel acrylamide electrophoresis under non-denaturing and denaturing conditions. The molecular weights of mitochondrial rRNAs (0.76-10-6 and 1.25-10-6) exceeded those of cytoplasmic rRNAs (0.67-10-6 and 1.19-10-6) when electrophoresed in 8 M urea at 60 degrees C. Electrophoresis in 1.1 M formaldehyde resulted in similar values except for heavy mitochondrial rRNA, which exhibited a higher molecular weight than observed in 8 M urea. The observed values for cytoplasmic rRNAs, especially the heavy component, represent a decrease from estimates obtained under non-denaturing conditions. This is the first report of the electrophoretic examination of higher plant rRNAs under denaturing conditions.