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PublicationStructural basis for oligomerization of auxin transcriptional regulators

Nature Communications No 5: 3617 – Parution : 2014

Nanao MH, Vinos-Poyo T, Brunoud G, Thevenon E, Mazzoleni M, Mast D, Laine S, Wang S, Hagen G, Li H, Guilfoyle TJ, Parcy F, Vernoux T and Dumas R
Structural basis for oligomerization of auxin transcriptional regulators.
Nature Communications, 2014, 5: 3617

Auxin is probably the most important plant hormone. It plays a role in most of the processes of growth and development at different stages of the life of the plant: embryo polarity, emergence of secondary roots, positioning flowers on the stem, fruit growth, directional growth towards the light, or against gravity.

All the molecular actors for perception and signaling of auxin have been identified. When the hormone concentration is low, ARF transcription factors (responsible for the induction of the gene by auxin) are kept inactive by the IAA inhibitors. When the auxin concentration is higher, IAA are degraded by the proteasome and induce ARF gene expression in response to auxin.

The interaction between ARF and IAA is at the heart of the auxin signaling and occurs via a domain (called domain III/IV) which is present in both the ARF and IAA. Its structure was previously unknown and it was thought to be a dimerization domain.
In collaboration with a team of ENS Lyon, a crystallographer at EMBL and American teams, we have solved the structure of the domain III/IV showed that it was a multimerization domain. This structure reveals the molecular basis of the assembly of ARF/ARF, IAA/IAA and ARF/IAA complexes. It also allowed to formulate a new hypothesis on the mode of action of IAA proteins: they could act by disrupting the cooperative binding of ARF multimers on genomic regions with multiple binding sites.

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