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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.
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http://dx.doi.org/10.7554/eLife.51787 | DOI Listing |
Elife
April 2020
Department of Crop Genetics, John Innes Centre, Norwich Research Park, Norwich, United Kingdom.
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.
View Article and Find Full Text PDFPlant J
March 2020
Division of Biological Science, Graduate School of Science, Nagoya University, Nagoya, Aichi, 464-8602, Japan.
In Arabidopsis, the ASYMMETRIC LEAVES2 (AS2) protein plays a key role in the formation of flat symmetric leaves via direct repression of the abaxial gene ETT/ARF3. AS2 encodes a plant-specific nuclear protein that contains the AS2/LOB domain, which includes a zinc-finger (ZF) motif that is conserved in the AS2/LOB family. We have shown that AS2 binds to the coding DNA of ETT/ARF3, which requires the ZF motif.
View Article and Find Full Text PDFPlant Biotechnol (Tokyo)
March 2018
Graduate School of Bioscience and Biotechnology, Chubu University, Kasugai, Aichi 487-8501, Japan.
Balanced development of adaxial and abaxial domains in leaf primordia is critical for the formation of flat symmetric leaf lamina. Arabidopsis ASYMMETRIC LEAVES1 (AS1) and AS2 proteins form a complex (AS1-AS2), which acts as key regulators for the adaxial development by the direct repression of expression of the abaxial gene / (/). Many modifier mutations have been identified, which enhance the defect of and mutations to generate abaxialized filamentous leaves without adaxial traits, suggesting that the development of the adaxial domain is achieved by cooperative repression by AS1-AS2 and the wild-type proteins corresponding to the modifiers.
View Article and Find Full Text PDFPLoS Biol
November 2009
Temasek Life Sciences Laboratory, National University of Singapore, Singapore.
The Arabidopsis homeotic protein AGAMOUS (AG), a MADS domain transcription factor, specifies reproductive organ identity during flower development. Using a binding assay and expression analysis, we identified a direct target of AG, GIANT KILLER (GIK), which fine-tunes the expression of multiple genes downstream of AG. The GIK protein contains an AT-hook DNA binding motif that is widely found in chromosomal proteins and that binds to nuclear matrix attachment regions of DNA elements.
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