Document Detail

Circadian regulation of chloroplast transcription in Chlamydomonas is accompanied by little or no fluctuation in RPOD levels or core RNAP activity.
MedLine Citation:
PMID:  23053955     Owner:  NLM     Status:  Publisher    
In Chlamydomonas growing under 24 h light-dark cycles, chloroplast transcription is under circadian clock control, and peaks early in the morning. The peak (but not trough) requires ongoing cytoplasmic translation, as it is sensitive to cycloheximide (CH). The chloroplast transcriptional apparatus in Chlamydomonas is simpler than in land plants, with only one type of RNA polymerase (RNAP, bacterial) and apparently only one sigma factor (RPOD). Core RNAP can be assayed in vitro with a non-sigma factor dependent template, and is sensitive to rifampicin. We developed a membrane-based assay for RNAP activity, and used it to determine that core activity is only weakly affected by pre-treating cells with CH. Moreover, core chloroplast RNAP activity was steady during a 24 h light-dark cycle. Levels of the sigma factor (RPOD) were examined using western blots, and found to fluctuate less than 25 % during light-dark cycles. These data indicate that circadian regulation of chloroplast transcription is distinct from regulation by sulfur availability, which involves significant changes in RPOD levels. The implications of this data for hypotheses that purport to explain the circadian control mechanism are discussed.
Ryo Kawazoe; Kristina M Mahan; Brad E Venghaus; Matthew L Carter; David L Herrin
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-10-10
Journal Detail:
Title:  Molecular biology reports     Volume:  -     ISSN:  1573-4978     ISO Abbreviation:  Mol. Biol. Rep.     Publication Date:  2012 Oct 
Date Detail:
Created Date:  2012-10-11     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0403234     Medline TA:  Mol Biol Rep     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Section of Molecular Cell & Developmental Biology, Institute for Cellular and Molecular Biology, University of Texas at Austin, Austin, TX, 78712, USA.
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