Dinoflagellate ribosomal RNA; an evolutionary relic?

The apparent molecular weights of the rRNA subunits of the dinoflagellate Peridinium cinctum fa. westii were determined by polyacrylamide gel electrophoresis to obtain an indication of its evolutionary status. The apparent molecular weights of the Peridinium light and heavy rRNA subunits were 0.7 and 1.23 X 10(6) respectively. The light rRNA is therefore typically eukaryotic but the heavy rRNA has a significantly lower MW than previously reported for higher eukaryotes which range from 1.3 to 1.75 X 10(6) depending on their evolutionary position. Thus by this criterion Peridinium is similar to red algae and may represent a eukaryotic stage, lower than fungi or green plants.