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Philippe Rieu

Molecular bases of the LEAFY-UFO synergy during floral development

Published on 3 February 2023
Thesis presented February 03, 2023

Flower development is crucial for the reproductive success of plants. This developmental step requires a deep genetic reprogramming, with the activation of flower-specific genes. In angiosperms, the LEAFY (LFY) Transcription Factor (TF) is a key regulator of flower development. Previous studies showed that LFY acts with cofactors that spatially specify its activity. The best-described LFY cofactor is the F-box protein UNUSUAL FLORAL ORGANS (UFO). However, how UFO regulates LFY’s activity at the molecular level remained unclear.
I first showed that the role of UFO as a component of an E3 ligase complex was not essential for its functions in planta. Then, I found that LFY and UFO act together by forming a complex that recognizes specific cis-elements. The structural characterization of this complex revealed that UFO binds both LFY and a precise DNA sequence, explaining its role as a transcriptional cofactor. Finally, preliminary data suggest that the formation of the LFY-UFO complex is conserved within angiosperms and non-flowering plants. Altogether, this study presents an original case in plant where an F-box protein acts mostly as a transcriptional cofactor through its ability to bind DNA.
A second part of my PhD was dedicated to the study of Arabidopsis LSH Oryza G1 (ALOG) genes, a plant-specific class of TFs regulated by LFY. Few data were available in the literature about their biochemical properties, and I focused on the interaction of the ALOG domain with DNA. I found that several ALOG proteins bind the same DNA motif and I characterized the DNA-binding mechanism.

Genetic, Integrated biology, Biochemistry

On-line thesis.