The molecular basis of flowering time regulation
File(s)
Author(s)
Charles, David
Type
Thesis or dissertation
Abstract
Flowering is controlled by a series of signals integrated to regulate gene expression and coordinate development. The flowering hormone FLOWERING LOCUS T (FT) positively regulates flowering while the highly homologous TERMINAL FLOWERING 1 (TFL1) negatively regulates flowering. FT is recruited to the promoter in a complex with FD, a transcription factor belonging to the bZIP family, and 14-3-3. This complex is called flowering activating complex (FAC). Here TFL1 is shown to form a complex with 14-3-3 proteins and FD that has striking similarity to the FAC. By probing the extended loop of TFL1 a small region was identified towards the N-terminus of the loop that is involved in mediating the interaction with 14-3-3. This TFL1–14-3-3 platform can interact with the C-terminus of FD, and moreover this interaction occurs between FD and 14-3-3 rather than directly between FD and TFL1 as had been previously speculated. Results indicate that the TFL1–14-3-3 complex, but not FT–14-3-3, can interact with the AP1 promoter from Arabidopsis and that FD is not required for this interaction. In addition, we have located a region of three residues near the C-terminal portion of the loop that when mutated can convert FT from an activator of flowering into a strong repressor of flowering in vivo. Overall, the results suggest that TFL1 can associate with DNA and recruit FD to specific regulatory sites via 14-3-3 proteins, while FT is recruited via FD to a different region within the AP1 promoter region. The data thus provide the basis for a mechanistic model for the antagonistic functions of FT and TFL1 in regulating flowering.
Version
Open Access
Date Issued
2013-09
Date Awarded
2014-02
Advisor
Turnbull, Colin
Zhang, Xiaodong
Sponsor
Biotechnology and Biological Sciences Research Council (Great Britain)
Publisher Department
Life Sciences
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)