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Regulation of arabidopsis catalase gene expression by light and the circadian clock.

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Call No.	QK495.C9 Z46 1996
Author	Zhong, HaiHong
Title	Regulation of arabidopsis catalase gene expression by light and the circadian clock.
Date	1996
Abstract	Circadian rhythms in a wide variety of cellular and metabolic processes are well documented in many organisms. An important step in understanding the molecular basis of the circadian clock is the characterization of clock-controlled genes. mRNA accumulation of two catalase genes, CAT2 and CAT3, in the higher plant, Arabidopsis thaliana, responds to organ-specific, developmental, temperature, and light signals, as well as to the circadian clock. Most strikingly, the circadian phases of maximal mRNA abundance for the two CAT genes are distinct, with CAT2 mRNA most abundant in the morning and CAT3 mRNA peaking in the evening. Thus, elements of the output pathways emanating from the circadian clock to regulate CAT2 and CAT3 expression must differ. The CAT3 genomic locus was isolated and characterized. Transgenic Arabidopsis containing CAT3-uidA fusions have been generated as a first step towards the identification of cellular components required for the circadian regulation of CAT3 gene. Elements within 745 bp upstream of the transcription start site are sufficient to drive GUS expression, and to confer appropriate developmental and organ-specific regulation on the GUS reporter. Rhythms in CAT mRNA abundance are detected in light-grown but not in etiolated seedlings. After illumination of etiolated seedlings, robust circadian oscillations develop immediately, following an acute induction of CAT2 and repression of CAT3. The magnitude of the acute induction of CAT2 varied according to the timing (circadian phase) of the onset of illumination, indicating that the clock is running in etiolated seedlings and regulates the responsiveness of CAT2 to light. When plants entrained under light-dark cycles are transferred into extended dark, oscillations in CAT2 continue, but damp to low levels, while oscillations in CAT3 in extended dark rapidly damp to high expression levels. Analysis of mutants with defects in photoperception establish that both Phytochrome A (PHYA) and the blue light receptor are necessary for the damping of CAT3 in extended dark and that HY5 is a component of the signal transduction pathway downstream of the photoreceptors. A model of light- and the clock-regulated pathways which control CAT2 and CAT3 expression is discussed.
Description	1 online resource
Format	application/pdf
Issuing Body	Dartmouth Dissertations are made available through the Dartmouth Digital Library.
Degree	Thesis (Ph.D)--Dartmouth College.
Copyright	In Copyright. This material is protected by copyright and/or related rights. You are free to use this material in any way that is permitted by copyright law that applies to your use. For other uses, you need to obtain permission from the rights-holder(s). http://rightsstatements.org/page/InC/1.0/
DOI	https://doi.org/10.1349/ddlp.2932

Title	zhong1996 1
Full Text	Regulation of Arabidopsis Catalase Gene Expression by Light and the Circadian Clock A Thesis Submitted to the Faculty in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Biological Sciences by HaiHong Zhong DARTMOUTH COLLEGE Hanover, New Hampshire June 1996

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Regulation of arabidopsis catalase gene expression by light and the circadian clock.

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