Phytochrome B inhibits binding of phytochrome-interacting factors to their target promoters
Article first published online: 25 SEP 2012
© 2012 The Authors. The Plant Journal © 2012 Blackwell Publishing Ltd
The Plant Journal
Volume 72, Issue 4, pages 537–546, November 2012
How to Cite
Park, E., Park, J., Kim, J., Nagatani, A., Lagarias, J. C. and Choi, G. (2012), Phytochrome B inhibits binding of phytochrome-interacting factors to their target promoters. The Plant Journal, 72: 537–546. doi: 10.1111/j.1365-313X.2012.05114.x
- Issue published online: 2 NOV 2012
- Article first published online: 25 SEP 2012
- Accepted manuscript online: 31 JUL 2012 10:56AM EST
- Received 24 May 2012; revised 17 July 2012; accepted 18 July 2012; published online 25 September 2012.
- phytochrome-interacting factors 3;
- phytochrome-interacting factors 1;
- DNA binding
Phytochromes are red and far-red light receptors in plants that mediate critical responses to light throughout the lifecycle. They achieve this in part by targeting negatively acting bHLH transcription factors called phytochrome-interacting factors (PIFs) for degradation within the nucleus. However, it is not known whether protein degradation is the primary mechanism by which phytochromes inhibit these repressors of photomorphogenesis. Here, we use chromatin immunoprecipitation to show that phyB inhibits the regulatory activity of PIF1 and PIF3 by releasing them from their DNA targets. The N-terminal fragment of phyB (NG-GUS-NLS; NGB) also inhibits binding of PIF3 to its target promoters. However, unlike full-length phyB, NGB does not promote PIF3 degradation, establishing the activity of NGB reflects its ability to inhibit PIF binding to DNA. We further show that Pfr forms of both full-length phyB and NGB inhibit DNA binding of PIF1 and PIF3 in vitro. Taken together, our results indicate that phyB inhibition of PIF function involves two separate processes: sequestration and protein degradation.