Abstract:
:DNA supercoiling in the chloroplast of the unicellular green alga Chlamydomonas reinhardtii was found to change with a diurnal rhythm in cells growing in alternating 12-h dark-12-h light periods. Highest and lowest DNA superhelicities occurred at the beginning and towards the end of the 12-h light periods, respectively. The fluctuations in DNA supercoiling occurred concurrently and in the same direction in two separate parts of the chloroplast genome, one containing the genes psaB, rbcL, and atpA and the other containing the atpB gene. Fluctuations were not confined to transcribed DNA regions, indicating simultaneous changes in DNA conformation all over the chloroplast genome. Because the diurnal fluctuations persisted in cells kept in continuous light, DNA supercoiling is judged to be under endogenous control. The endogenous fluctuations in chloroplast DNA topology correlated tightly with the endogenous fluctuations of overall chloroplast gene transcription and with those of the pool sizes of most chloroplast transcripts analyzed. This result suggests that DNA superhelical changes have a role in the regulation of chloroplast gene expression in Chlamydomonas.
journal_name
Mol Cell Bioljournal_title
Molecular and cellular biologyauthors
Salvador ML,Klein U,Bogorad Ldoi
10.1128/mcb.18.12.7235subject
Has Abstractpub_date
1998-12-01 00:00:00pages
7235-42issue
12eissn
0270-7306issn
1098-5549journal_volume
18pub_type
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