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Abstract Detail


Plant Photoreceptors and Photomorphogenesis

Ong, May S. [1], Knowles, Stephen M. [1], Lu, Sheen X. [1], Tobin, Elaine M. [2].

Photoreceptors and circadian rythmns in arabidopsis.

The transcription factors CCA1 and LHY have been proposed to be components of the central oscillator in plants. We have obtained evidence that a pulse of CCA1 can reset rhythms, thus firmly establishing it as an oscillator component. We have found that phytochrome regulates the expression of CCA1 and LHY and have now tested the contribution of phyA and phyB to the transcription of CCA1 and LHY. In etiolated seedlings phyA is the major phytochrome responsible for the acute response, but phyB affects the circadian accumulation of the two RNAs. How do CCA1 and LHY regulate target genes? LHY binds to the same region of the Lhcb promoter as CCA1. In chromatin immunoprecipitations, they are found associated with the promoters of Lhcb genes, which are most highly expressed in the morning, and also with the promoter of CCR2, a gene that is most highly expressed in the evening. This observation suggested that CCA1 and LHY could be involved in both positive and negative regulation of transcription. We also found that the activity of CCA1 depends in part on the time at which a pulse of CCA1 is given.


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1 - University of California at Los Angeles, Dept Molecular , Cell, and Developmental Biology, Los Angeles, CA, 90095, USA
2 - University of California, Los Angeles, Molecular, Cell and Developmental Biology

Keywords:
photoreceptor
photogenesis
Arabidopsis
oscillator
Phytochrome A & B
CCA1
LHY
transcription factor.

Presentation Type: Symposium or Colloquium Presentation
Session: SY04
Location: Boulevard C/Hilton
Date: Monday, July 9th, 2007
Time: 8:30 AM
Number: SY04001
Abstract ID:887


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