Davies, Siân Elizabeth Wynne (2013) Transcription factor interactions at the promoter of the Arabidopsis circadian clock gene LHY. PhD thesis, University of Warwick.

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Abstract

The circadian clock is the endogenous mechanism by which a wide variety of
biological processes are regulated in anticipation of daily changes in the external
environment. In Arabidopsis thaliana, the clock comprises a number of complex gene
and protein interactions, involving multiple regulatory feedback loops. The clock gene
LHY has a central role in these loops, activating and repressing morning- and evening-
expressed genes respectively. These clock genes in turn sequentially repress the
expression of LHY throughout the day and night, restricting it to a sharp
transcriptional peak at dawn. However, the molecular mechanisms of these regulatory
interactions with the LHY promoter were not known. Therefore, this project first
aimed to determine which promoter motifs are responsible for mediating regulation of
LHY circadian expression. This was achieved through luciferase assays with mutated
pLHY:LUC reporter constructs, which identified the CT-rich region as responsible for
rhythmic expression of LHY, and the G-box as mediating regulation by the clock
protein TOC1. Since few regulators were known to target the LHY promoter, this
project also aimed to identify transcription factors binding the promoter using a Yeast
One-Hybrid assay. Transcription factors with roles in a wide variety of biological
pathways were identified from this screen, with abiotic stress and plant defence
pathways particularly well-represented. In addition, a number of antagonistic and
synergistic regulatory interactions were established as occurring between stress
factors and clock proteins at specific promoter motifs. We can therefore conclude that
LHY is regulated by a complex network of transcription factor interactions, enabling
the rapid integration of environmental stress signals into the clock.

Item Type:	Thesis or Dissertation (PhD)
Subjects:	Q Science > QH Natural history > QH301 Biology Q Science > QH Natural history > QH426 Genetics
Library of Congress Subject Headings (LCSH):	Arabidopsis thaliana , Circadian rhythms , Plant genetics
Official Date:	January 2013
Dates:	Date Event January 2013 Submitted
Institution:	University of Warwick
Theses Department:	School of Life Sciences
Thesis Type:	PhD
Publication Status:	Unpublished
Supervisor(s)/Advisor:	Carré, Isabelle
Extent:	xvi, 181 leaves : illustrations
Language:	eng

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