TITLE>Herrmann RG et al. 1975
Herrmann RG et al. 1975
- Authors:
Herrmann, RG. Bohnert HJ. Kowallik KV. Schmitt JM.
- Title:
Size, conformation and purity of chloroplast DNA of some higher plants.
- Reference location:
Biochimica et Biophysica Acta. 378(2):305-17, 1975 Jan 20.
- Abstract:
1. Chloroplast DNA of Antirrhinum majus, Oenothera hookeri, Beta vulgaris
and Spinacia oleracea band at the same buoyant density of 1.697 g-cm-3 in
neutral CsCl equilibrium gradients. The corresponding nuclear DNAs band at
1.691, 1.703, 1.695 and 1.695 g-cm-3, respectively. The purity of
chloroplast and nuclear DNA can be assessed objectively only in the cases
of Antirrhinum and Oenothera. 2. Electron microscopic analysis of
chloroplast DNA, purified in CsCl or CsCl/ethidium bromide gradients,
revealed up to 80% circular molecules. Of these about 15% were of
supertwisted conformation. Best yields of circular molecules were
recovered when populations of unbroken chloroplasts were subjected to
DNAase and phosphodiesterase treatment, and when the DNA was purified from
viscous lysates by centrifugation into a CsCl cushion. Treatment of
plastids with DNAase alone did not guarantee complete degradation of
nuclear DNA. 3. The average contour length of the open circular
chloroplast DNA molecules was basically similar for all four plants. They
were 45.9 plus or minus 2.1 mum for Antirrhinum, 45.7 plus or minus 1.9
mum for Spinacia, 44.9 plus or minus 1.7 mum for Beta and 45.2 mum for
Oenothera. This is comparable to the size derived for the coding capacity
of chloroplast DNA from reassociation experiments. As much as 15% of the
total population of circles in chloroplast DNA of Spinacia were circular
dimers.
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