The Synthesis and Stability of Ribosomal RNA in Blue‐Green Algae

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Abstract
The ribosomal RNAs of the blue‐green algae Tolypothrix distorta, Anabaena cyclindrica and Nostoc muscorum have average molecular weights (Mr) of 1.1 × 106 and 0.56 × 106 as determined by acrylamide gel electrophoresis. The larger‐molecular‐weight rRNA is unstable and breaks down to yield a fragment of Mr approximately 0.9 × 106. Pulse‐labelling experiments show that no single high‐molecular‐weight polycistronic precursor to the rRNAs can be detected. The rRNA with Mr 1.1 × 106 is synthesized via a precursor molecule of Mr approximately 1.22 × 106, whilst there are apparently two sequential precursors to the rRNA with Mr 0.56 × 106 having Mr 0.76 × 106 and 0.68 × 106. The DNA of all the blue‐green algae was fractionated into two components on the gels. The significance of this behaviour is not yet understood.