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Regulation of Nuclear DNA Replication by the Chloroplast in Chlamydomonas

John Blamire, Valerie R. Flechtner and Ruth Sager
Proceedings of the National Academy of Sciences of the United States of America
Vol. 71, No. 7 (Jul., 1974), pp. 2867-2871
Stable URL: http://www.jstor.org/stable/63669
Page Count: 5
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Regulation of Nuclear DNA Replication by the Chloroplast in Chlamydomonas
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Abstract

The experiments described in this paper implicate chloroplast protein synthesis in the regulation of nuclear DNA replication. The inhibition of nuclear DNA replication in the lower eukaryote, Chlamydomonas reinhardi strain 21gr, was examined after growth of cells with a series of antibiotics (streptomycin, neamine, spectinomycin, cleocin, chloramphenicol, and rifampicin) each of which has a known effect upon chloroplast RNA or protein synthesis in this organism. Each antibiotic inhibited nuclear DNA replication at drug concentrations at which there was little or no inhibition of adenine incorporation into chloroplast DNA. That chloroplast DNA was replicating under these conditions rather than merely being repaired, was shown first by the high incorporation rates and second by a 14N-15N density transfer experiment in which chloroplast DNA doubled in the presence of streptomycin, while no incorporation into nuclear DNA was detected. A small DNA peak, Component III, located between nuclear and chloroplast DNA's in CsCl gradients, possibly mitochondrial, was more pronounced in DNA from antibiotic-inhibited cultures than from controls.

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