Nucleinsäuren in Chloroplasten I. Charakterisierung der DNS und RNS von Antirrhinum majus

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Abstract
Chloroplast preparations isolated from freeze-dried leaves in a non-aqueous medium contain DNA. Characterization of the DNA was based on chemical analyses and density gradient centrifugation. The chloroplast DNA has a density of 1.698 g/cm3 corresponding to a guanine-cytoslne content of 37-38%. The hyperchromic effect of the DNA revealed its double-stranded structure. Leaf DNA also has been characterized by density gradient centrifugation and is a major component of the nuclear DNA with a density of 1.689 g/cm3 which corresponds to a guanine-cytoslne content of about 31% and a minor component identified as chloroplast DNA. Extraction of the total nucleic acids of chloroplast preparations and their chromatographic separation on methylated serum albumin column yielded 5 fractions as follows: soluble RNA with s = 3.8 - 4.0, DNA containing small but detectable amounts of an unknown RNA component, 2 RNA fractions presumably of ribosomal origin with s = 17 and s = 26, and a RNA fraction heterogeneous in molecular size with s = 23-50. The soluble RNA has a high guanine-cytosine content whereas the preceding fraction has a relatively high adenine content. Compared with the nucleic acids from leaves, the chloroplast preparations contain the same fractions and differ only in the higher fraction III content in relation to the amount in fraction IV. In addition to the DNA fraction of leaf extract with the sedimentation coefficient of s = 12-15, a further UV-light absorbing component with s = 5.0-5.5 was found. Its character is unknown.