A non-DNA-binding activity for the ATHB4 transcription factor in the control of vegetation proximity.
In plants, perception of vegetation proximity by phytochrome photoreceptors activates a transcriptional network that implements a set of responses to adapt to plant competition, including elongation of stems or hypocotyls. In Arabidopsis thaliana, the homeodomain-leucine zipper (HD-Zip) transcription factor ARABIDOPSIS THALIANA HOMEOBOX 4 (ATHB4) regulates this and other responses, such as leaf polarity. To better understand the shade regulatory transcriptional network, we have carried out structure-function analyses of ATHB4 by overexpressing a series of truncated and mutated forms and analyzing three different responses: hypocotyl response to shade, transcriptional activity and leaf polarity. Our results indicated that ATHB4 has two physically separated molecular activities: that performed by HD-Zip, which is involved in binding to DNA-regulatory elements, and that performed by the ETHYLENE-RESPONSIVE ELEMENT BINDING FACTOR-associated amphiphilic repression (EAR)-containing N-terminal region, which is involved in protein-protein interaction. Whereas both activities are required to regulate leaf polarity, DNA-binding activity is not required for the regulation of the seedling responses to plant proximity, which indicates that ATHB4 works as a transcriptional cofactor in the regulation of this response. These findings suggest that transcription factors might employ alternative mechanisms of action to regulate different developmental processes.
['Gallemí|Marçal|M|', 'Molina-Contreras|Maria Jose|MJ|', 'Paulišić|Sandi|S|', 'Salla-Martret|Mercè|M|', 'Sorin|Céline|C|', 'Godoy|Marta|M|', 'Franco-Zorrilla|Jose Manuel|JM|', 'Solano|Roberto|R|', 'Martínez-García|Jaime F|JF|']
D017360:Arabidopsis D029681:Arabidopsis Proteins D018744:DNA, Plant D018506:Gene Expression Regulation, Plant D018398:Homeodomain Proteins D018546:Hypocotyl D019913:Nuclear Localization Signals D018515:Plant Leaves D030821:Plants, Genetically Modified D054730:Protein Interaction Domains and Motifs D012097:Repressor Proteins D036226:Seedlings D014157:Transcription Factors
transcription factors Arabidopsis thaliana homeodomain-leucine zipper ARABIDOPSIS THALIANA HOMEOBOX 4 (ATHB4) DNA-binding activity transcriptional cofactors ETHYLENE-RESPONSIVE ELEMENT BINDING FACTOR-associated amphiphilic repression (EAR) motif shade avoidance syndrome