5/28/2023 0 Comments Srdx hda19 tplThis is realised by interaction with Aux/IAA repressors, leading to their ubiquitination and subsequent degradation by the 26S proteasome, ultimately relieving the repression of ARF-targeted loci ( Kelley and Estelle, 2012 Leyser, 2018 Weijers and Wagner, 2016). The main role of this auxin perception mechanism, besides non-transcriptionally inhibiting growth ( Fendrych et al., 2018 Gallei et al., 2019), is transcriptional reprogramming. As auxin levels increase, the auxin molecule binds to members of the TIR1/AFB family of auxin co-receptors ( Kepinski and Leyser, 2005 Dharmasiri et al., 2005). In canonical auxin signalling, auxin-responsive genes are repressed when auxin levels are low by Aux/IAA transcriptional repressors that interact with DNA-bound Auxin Response Factors (ARFs). In plants, this coordination can be facilitated by phytohormones such as auxin, which controls processes throughout plant development ( Vanneste and Friml, 2009). Changes in gene expression are often controlled by mobile signals that translate positional information into cell type-specific transcriptional outputs ( Hironaka and Morishita, 2012). Tight temporal and spatial regulation of the genes involved in these processes is essential for proper development of the organism. a fertilised oocyte) that proliferates into numerous cells ultimately differentiating to make up specialised tissues and organs. Introductionĭevelopmental programmes within multicellular organisms originate from a single cell ( i.e. 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. 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. 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. 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. In contrast, plant hormone signalling is most commonly based on de-repression via the degradation of transcriptional repressors. These results suggested that integrating activation of BR-signaling pathways with the formation of the protein complex containing BES1/BZR1 and TPL–HDA19 via the EAR motif was important in fine-tuning BR-related gene networks in plants.Hormonal signalling in animals often involves direct transcription factor-hormone interactions that modulate gene expression. In addition to BR-related gene expression, the BES1–HDA19 transcription factor complex was important for abiotic stress-related drought stress tolerance and organ boundary formation. RNA-sequencing analysis of Arabidopsis plants over-expressing bes1-DmEAR or bes1-DmEAR-HDA19 revealed an essential role for HDA19 activity in regulation of BES1/BZR1-mediated BR signaling. Defects in BR-related functions of BES1 and BZR1 proteins containing a mutated EAR motif were completely rescued by artificial fusion with EAR-repression domain (SRDX), TOPLESS (TPL), or HDA19 proteins. We here report that formation of a protein complex between BES1 and BZR1 and Histone Deacetylase 19 (HDA19) via the conserved ERF-associated amphiphilic repression (EAR) motif proved essential for regulation of BR-signaling-related gene expression. In Arabidopsis thaliana, the BR-related transcription factors BRI1-EMS-SUPPRESSOR 1 (BES1) and BRASSINAZOLE-RESISTANT 1 (BZR1) regulate a range of global gene expression in response to BR and several external signaling cues however, the molecular mechanisms by which they mediate the reprogramming of downstream transcription remain unclear. Brassinosteroids (BRs) are plant steroid hormones that are essential for diverse growth and developmental processes across the whole life cycle of plants. 1371-1377 ISSN: 0032-0935 Subject: Arabidopsis thaliana, brassinosteroids, drought tolerance, gene expression, gene regulatory networks, histone deacetylase, sequence analysis, signal transduction, steroid hormones, transcription (genetics), transcription factors Abstract: MAIN CONCLUSION: The brassinosteroid-related BES1 and BZR1 transcription factors dynamically modulate downstream gene networks via the TPL–HDA19 co-repressor complex in BR-signaling pathways in Arabidopsis thaliana. Transcriptional network regulation of the brassinosteroid signaling pathway by the BES1–TPL–HDA19 co-repressor complex Author: Hyemin Kim, Donghwan Shim, Suyun Moon, Jinsu Lee, Wonsil Bae, Hyunmo Choi, Kyunghwan Kim, Hojin Ryu Source: Planta 2019 v.250 no.4 pp.
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