SALT TOLERANCE HOMOLOG2, a B-Box Protein in Arabidopsis That Activates Transcription and Positively Regulates Light-Mediated Development
- 1 October 2007
- journal article
- Published by Oxford University Press (OUP) in Plant Cell
- Vol. 19 (10), 3242-3255
- https://doi.org/10.1105/tpc.107.054791
Abstract
CONSTITUTIVELY PHOTOMORPHOGENIC1 (COP1) and ELONGATED HYPOCOTYL5 (HY5) are two major regulators of light signaling in plants. Here, we identify SALT TOLERANCE HOMOLOG2 (STH2) as a gene that interacts genetically with both of these key regulators. STH2 encodes a B-box–containing protein that interacts physically with HY5 in yeast and in plant cells. Whereas STH2 is uniformly nuclear by itself, it shows a COP1-dependent localization to speckles when coexpressed with COP1. We identified two independent T-DNA insertion lines in STH2. Both alleles are hyposensitive to blue, red, and far-red light. The sth2 mutant, like hy5, shows an enhanced number of lateral roots and accumulates less anthocyanin. Analysis of double mutants between sth2 and hy5 indicates that STH2 has both HY5-dependent and -independent functions. Furthermore, besides partially suppressing the hypocotyl phenotype of dark-grown cop1 alleles, sth2 also suppresses the reduced number of lateral roots and high anthocyanin levels in light-grown cop1 alleles. Interestingly, we found that STH2 can activate transcription. Transient transfection assays in protoplasts using a LUC reporter driven by the chalcone isomerase promoter show that the B-boxes in STH2 and a functional G-box element in the promoter are required for this activity. In conclusion, we have identified STH2, a B-box protein in Arabidopsis thaliana, as a positive regulator of photomorphogenesis and report that the B-box domain plays a direct role in activating transcription in plants.Keywords
This publication has 57 references indexed in Scilit:
- Solution Structure of the MID1 B-box2 CHC(D/C)C2H2 Zinc-binding Domain: Insights into an Evolutionarily Conserved RING FoldJournal of Molecular Biology, 2007
- Analysis of Transcription Factor HY5 Genomic Binding Sites Revealed Its Hierarchical Role in Light Regulation of DevelopmentPlant Cell, 2007
- CONSTANS and the CCAAT Box Binding Complex Share a Functionally Important Domain and Interact to Regulate Flowering ofArabidopsisPlant Cell, 2006
- Solution Structure of the RBCC/TRIM B-box1 Domain of Human MID1: B-box with a RINGJournal of Molecular Biology, 2006
- Opposite Root Growth Phenotypes of hy5 versus hy5 hyh Mutants Correlate with Increased Constitutive Auxin SignalingPLoS Genetics, 2006
- Identification of Promoter Motifs Involved in the Network of Phytochrome A-Regulated Gene Expression by Combined Analysis of Genomic Sequence and Microarray DataPlant Physiology, 2003
- A Genome-Wide Analysis of Blue-Light Regulation of Arabidopsis Transcription Factor Gene Expression during Seedling DevelopmentPlant Physiology, 2003
- Regulation of Arabidopsis cryptochrome 2 by blue-light-dependent phosphorylationNature, 2002
- The Roles of Photoreceptor Systems and the COP1-Targeted Destabilization of HY5 in Light Control of Arabidopsis Seedling DevelopmentPlant Physiology, 2000
- Photomorphenesis: Seeing the light in plant developmentCurrent Biology, 1995