Ribosomal ribonucleic acid and ribosomal precursor ribonucleic acid in Anacystis nidulans

Abstract

The RNA of the blue–green alga Anacystis nidulans contains three ribosomal RNA species with molecular weights of 0.56×106, 0.9×106, and 1.1×106if the RNA is extracted in the absence of Mg2+. The 0.9×106mol.wt. rRNA is extremely slowly labelled in32P-incorporation experiments. This rRNA may be a cleavage product of the 1.1×106mol.wt. rRNA from the ribosomes of cells in certain physiological states (e.g. light-deficiency during growth). The cleavage of the 1.1×106mol.wt. rRNA during the extraction procedure can be prevented by the addition of 10mm-MgCl2.32P-pulse-labelling studies demonstrate the rapid synthesis of two ribosomal precursor RNA species. One precursor RNA migrating slightly slower than the 1.1×106mol.wt. rRNA appears much less stable than the other precursor RNA, which shows the electrophoretic behaviour of the 0.7×106mol.wt. rRNA. Our observations support the close relationship between bacteria and blue–green algae also with respect to rRNA maturation. The conversion of the ribosomal precursor RNA species into 0.56×106- and 1.1×106-mol.wt. rRNA species requires Mg2+in the incubation medium.