Abstract
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.
Highlights
Light is an important factor for plant growth and development
GBF1, HY5, and HYH have previously been shown to bind to the G-box light-responsive element present in the RBCS-1A minimal promoter, and HY5 and HYH form a heterodimer at this element [19, 23, 26]
The level of enrichment of the RBCS-1A promoter fragment was reduced to about 5-fold in the transgenic hy5 mutant background; it remained at a similar level in transgenic hyh mutants. These results demonstrate that GBF1 and HY5 proteins form a heterodimer at the G-box of RBCS-1A promoter in BL-grown Arabidopsis seedlings
Summary
Light is an important factor for plant growth and development. Results: GBF1 interacts with two other bZIP proteins, HY5 and HYH, in light signaling. Arabidopsis bZIP transcription factor, GBF1, acts as a differential regulator of cryptochrome-mediated blue light signaling. The synergism between red and blue light for control of gene expression and seedling development has been reported where HY5 and HYH were found to enhance the phyB signaling output [24]. Both of these proteins are degraded by COP1-mediated proteasomal pathways in the dark [13, 23]. The examination of physiological functions of GBF1 has revealed that it functions in cryptochrome-mediated blue light signaling and plays a differential regulatory role in Arabidopsis seedling development [27]. Investigated the genetic and molecular relationships of GBF1 with HY5 and HYH in Arabidopsis seedling development
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
