Molecular integrity of chloroplast ribosomal ribonucleic acid.
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ABSTRACT:
SUBMITTER: Leaver CJ
PROVIDER: S-EPMC1165809 | biostudies-other | 1973 Sep
REPOSITORIES: biostudies-other
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Project description:Instability of chloroplast rRNA has been observed with essentially all chloroplast RNA preparations. This paper describes experiments that show that, under normal conditions of preparation and fractionation, only the heavy chloroplast component (mol.wt. 1.1x10(6)) is unstable, the light chloroplast rRNA (mol.wt. 0.56x10(6)) and the cytoplasmic rRNA species (mol.wt. 1.3x10(6) and 0.70x10(6)) being stable. The stability of the 1.1x10(6)-mol. wt. molecule varies with different plant species, as also does the size and the number of fragments produced. Cleavages in three particular regions of the molecule are very frequent within the range of tissues studied. The 1.1x10(6)-mol.wt. rRNA is, however, stabilized by the presence of Mg(2+) during the preparation and fractionation of the RNA.
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Project description:Chloroplast rRNA synthesis was studied in spinach leaf tissue cultured under sterile conditions which eliminate bacterial rRNA synthesis. The synthesis was inhibited by darkness, but concomitant cytoplasmic rRNA synthesis was unaffected. A complex pattern of labelled rRNA precursors was found in extracts from cultured leaf tissue by using polyacrylamide-gel electrophoresis. However, differences between the precursor profiles of leaf tissue cultured in the light and in the dark could not be correlated with chloroplast rRNA synthesis since large amounts of high-molecular-weight precursors of cytoplasmic rRNA dominated the pattern in both cases. A double-isotope-labelling technique was used, which enabled light-stimulated rRNA synthesis to be studied in whole leaf tissue. Two rapidly labelled RNA species of molecular weights 1.15x10(6) and 0.65x10(6) were detected, which were thought to have possible precursor significance in the synthesis of mature chloroplast rRNA of molecular weights 1.04x10(6) and 0.56x10(6) respectively. Cycloheximide treatment resulted in the accumulation of RNA of molecular weight 1.8x10(6), whose function is unknown.
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Project description:Evidence for the sequence of duckweed (Lemna minor) chloroplast 5S rRNA was derived from the analysis of partial and complete enzymic digests of the 32P-labelled molecule. The possible sequence of the chloroplast 5S rRNA from three other flowering plants was deduced by complete digestion with T1 ribonuclease and comparison of the sequences of the oligonucleotide products with homologous sequences in the duckweed 5S rRNA. This analysis indicates that the chloroplast 5S rNA species differ appreciably from their cytosol counterparts but bear a strong resemblance to one another and to the 5S rRNA species of prokaryotes. Structural features apparently common to all 5S rRNA molecules are also discussed.
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Project description:Green leaves of the broad bean (Vicia faba) contain two 5S RNA components that can be separated from each other by polyacrylamide-gel electrophoresis. The major component is located in the larger subunit of cytoplasmic ribosomes, whereas the minor component occurs in the larger subunit of chloroplast ribosomes. Their electrophoretic mobilities relative to those of Escherichia coli 5S RNA (120 nucleotides) and plant 4S RNA (78 nucleotides) suggest that they consist of 118 and 122 nucleotide residues respectively. Thermal ;melting' profiles of plant cytoplasmic and chloroplast 5S RNA species at 260nm indicate the similarity of their secondary structures, not only to each other, but also to those of E. coli and mammalian 5S RNA species. The base compositions of the two plant 5S RNA species have more in common with each other than with the corresponding molecules from either E. coli or mammalian cells.
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Project description:The RNA of the blue-green alga Anacystis nidulans contains three ribosomal RNA species with molecular weights of 0.56x10(6), 0.9x10(6), and 1.1x10(6) if the RNA is extracted in the absence of Mg(2+). The 0.9x10(6)mol.wt. rRNA is extremely slowly labelled in (32)P-incorporation experiments. This rRNA may be a cleavage product of the 1.1x10(6)mol.wt. rRNA from the ribosomes of cells in certain physiological states (e.g. light-deficiency during growth). The cleavage of the 1.1x10(6)mol.wt. rRNA during the extraction procedure can be prevented by the addition of 10mm-MgCl(2). (32)P-pulse-labelling studies demonstrate the rapid synthesis of two ribosomal precursor RNA species. One precursor RNA migrating slightly slower than the 1.1x10(6)mol.wt. rRNA appears much less stable than the other precursor RNA, which shows the electrophoretic behaviour of the 0.7x10(6)mol.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 0.56x10(6)- and 1.1x10(6)-mol.wt. rRNA species requires Mg(2+) in the incubation medium.
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Project description:1. A method for the extraction of plant nucleic acids and their separation on methylated-serum-albumin-kieselguhr columns is described. It is demonstrated that the characteristics of the elution profiles of material from the same source are consistently reproducible. 2. Major dissimilarities were found in the elution profiles of nucleic acids from root and from leaves of Vicia faba L. These dissimilarities were confirmed by polyacrylamide-gel electrophoresis. 3. Four distinct types of low-molecular-weight RNA were demonstrated to be present in leaves, clearly distinguished by their behaviour when chromatographed on methylated-serum-albumin-kieselguhr columns. (a) Both cytoplasmic and chloroplast ribosomes contained a low-molecular-weight RNA, and these components were distinct from each other. (b) The chloroplast possessed a unique ;soluble' RNA (i.e. RNA that is not precipitated by centrifugal forces that sediment ribosomes) which was not present in the rest of the cell. (c) A soluble component, probably transfer RNA, was found in both the chloroplasts and in the cytoplasm. 4. The components distinguishable by methylated-serum-albumin-kieselguhr column chromatography could not be distinguished by sucrose-density-gradient centrifugation.
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Project description:1. Ribosomal RNA has been prepared by extracting tissues with a phenol-cresol mixture, and ribosomal RNA can be selectively precipitated with m-cresol. No rapidly labelled RNA was associated with this material. 2. However, if RNA and DNA are extracted with 4-aminosalicylate and phenol-cresol mixture and the nucleic acids precipitated, DNA, glycogen and s-RNA (transfer RNA) can be extracted with 3m-sodium acetate and in this case rapidly labelled RNA remains associated with the ribosomal RNA. 3. The ribosomal RNA is stable in the presence of concentrated salt solution and, although the secondary structure is lost by heating at 70 degrees in 10mm-sodium acetate, it can be re-formed in the presence of 200mm-sodium acetate. 4. The 28s and 18s components have been separated and their base compositions determined.
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