Journal
PLANT CELL
Volume 20, Issue 9, Pages 2324-2338Publisher
OXFORD UNIV PRESS INC
DOI: 10.1105/tpc.108.061747
Keywords
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Funding
- The Swedish Research Council
- Magnus Bergvalls Foundation
- Royal Physiographic Society in Lund
- Royal Swedish Academy of Agriculture and Forestry
- Adlerbert Research Foundation
- Carl Trygger Foundation
- Swedish South Asia Studies Network
- Wenner-Gren foundation
- Spanish Ministry of Science and Innovation (MICINN)
- Comunidad de Madrid [S-GEN/0191/2006]
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B-box containing proteins play an important role in light signaling in plants. Here, we identify LIGHT-REGULATED ZINC FINGER1/SALT TOLERANCE HOMOLOG3 (STH3), a B-box encoding gene that genetically interacts with two key regulators of light signaling, ELONGATED HYPOCOTYL5 (HY5) and CONSTITUTIVE PHOTOMORPHOGENIC1 (COP1). STH3 physically interacts with HY5 in vivo and shows a COP1-dependent localization to nuclear speckles when coexpressed with COP1 in plant cells. A T-DNA insertion mutant, sth3, is hyposensitive to high fluence blue, red, and far-red light and has elongated hypocotyls under short days. Analyses of double mutants between sth3, sth2, and hy5 suggest that they have partially overlapping functions. Interestingly, functional assays in protoplasts suggest that STH3 can activate transcription both independently and together with STH2 through the G-box promoter element. Furthermore, sth3 suppresses the cop1 hypocotyl phenotype in the dark as well as the anthocyanin accumulation in the light. Finally, COP1 ubiquitinates STH3 in vitro, suggesting that STH3 is regulated by COP1. In conclusion, we have identified STH3 as a positive regulator of photomorphogenesis acting in concert with STH2 and HY5, while also being a target of COP1-mediated ubiquitination.
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