Ribosomal RNA synthesis in plants

Abstract

The cytoplasmic ribosomal RNA's (of molecular weight 1.3 × 10 6 and 0.7 × 10 6 daltons) of higher plants arise by the selective cleavage of larger precursor molecules. The main precursor RNA species in carrot ( Daucus carota) have been tentatively characterized by polyacrylamide-gel electrophoresis as having molecular weights of 2.8 × 10 6, 2.2 × 10 6 and 1.4 × 10 6 daltons, and base compositions similar to ribosomal RNA. Results obtained using isotope labeling combined with cell-fractionation techniques have shown that these molecules are localized in the nucleus and have kinetics of synthesis consistent with them being precursors of ribosomal RNA.