Ribonucleic Acid Synthesis in Plants
The two large RNA components of the ribosomes of the plant cytoplasm have molecular weights of 1.3 and 0.7 x 106. These molecules are synthesized in the nucleolus as part of a polycistronic precursor which is subsequently methylated and cleaved in a number of processing steps to produce functional rRNA (1). Polyacrylamide gel electrophoresis of pulse-labelled RNA from the nuclei of aseptically grown Phaseolus aureus seedlings shows that the rRNA precursors and processing intermediates have molecular weights of approximately 2.6, 1.45, and 1.0 x 106. The precursors have a similar base composition to rRNA and competitive hybridi-zation experiments show that the large precursor contains sequences for both the 1.3 and 0.7 x 106 molecular weight rRNAs (2). Saturation hybridization experiments between rRNA and nuclear DNA shows that 0.6–0.9% of the DNA codes for rRNA.
KeywordsHybridization Experiment Processing Intermediate Acer Pseudoplatanus Large Precursor Diploid Nucleus
- 1.Grierson, D., Rogers, M.E., Sartirana, M.L., and Loening, U.E. (1970) Cold Spring Harbor Symp. Quant. Biol. 35, 589–598.Google Scholar