Molecular Interactions of GBF1 with HY5 and HYH Proteins during Light-mediated Seedling Development in Arabidopsis thaliana*

Aparna Singh,Hathi Ram,N. Abbas,Sudip Chattopadhyay

Published 2012 in Journal of Biological Chemistry

ABSTRACT

Background: Light is an important factor for plant growth and development. Results: GBF1 interacts with two other bZIP proteins, HY5 and HYH, in light signaling. Conclusion: This work demonstrates the functional interconnections of GBF1, HY5, and HYH. Significance: The knowledge gained in this study will help to understand light-controlled plant growth and development. Arabidopsis bZIP transcription factor, GBF1, acts as a differential regulator of cryptochrome-mediated blue light signaling. Whereas the bZIP proteins, HY5 (elongated hypocotyl 5) and HYH (HY5 homologue), are degraded by COP1-mediated proteasomal pathways, GBF1 is degraded by a proteasomal pathway independent of COP1. In this study, we have investigated the functional interrelations of GBF1 with HY5 and HYH in Arabidopsis seedling development. The genetic studies using double and triple mutants reveal that GBF1 largely acts antagonistically with HY5 and HYH in Arabidopsis seedling development. Further, GBF1 and HY5 play more important roles than HYH in blue light-mediated photomorphogenic growth. This study reveals that GBF1 is able to form a G-box-binding heterodimer with HY5 but not with HYH. The in vitro and in vivo studies demonstrate that GBF1 co-localizes with HY5 or HYH in the nucleus and physically interacts with both of the proteins. The protein-protein interaction studies further reveal that the bZIP domain of GBF1 is essential and sufficient for the interaction with HY5 or HYH. Taken together, these data demonstrate the functional interrelations of GBF1 with HY5 and HYH in Arabidopsis seedling development.

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