Direct ETTIN-auxin interaction controls chromatin states in gynoecium development.

André Kuhn, Sigurd Ramans Harborough, Heather M McLaughlin, Bhavani Natarajan, Inge Verstraeten, Jiří Friml, Stefan Kepinski, Lars Østergaard

eLife 2020 Apr 08

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Hormonal signalling in animals often involves direct transcription factor-hormone interactions that modulate gene expression. In contrast, plant hormone signalling is most commonly based on de-repression via the degradation of transcriptional repressors. Recently, we uncovered a non-canonical signalling mechanism for the plant hormone auxin whereby auxin directly affects the activity of the atypical auxin response factor (ARF), ETTIN towards target genes without the requirement for protein degradation. Here we show that ETTIN directly binds auxin, leading to dissociation from co-repressor proteins of the TOPLESS/TOPLESS-RELATED family followed by histone acetylation and induction of gene expression. This mechanism is reminiscent of animal hormone signalling as it affects the activity towards regulation of target genes and provides the first example of a DNA-bound hormone receptor in plants. Whilst auxin affects canonical ARFs indirectly by facilitating degradation of Aux/IAA repressors, direct ETTIN-auxin interactions allow switching between repressive and de-repressive chromatin states in an instantly-reversible manner. © 2020, Kuhn et al.

Citation

André Kuhn, Sigurd Ramans Harborough, Heather M McLaughlin, Bhavani Natarajan, Inge Verstraeten, Jiří Friml, Stefan Kepinski, Lars Østergaard. Direct ETTIN-auxin interaction controls chromatin states in gynoecium development. eLife. 2020 Apr 08;9