Plant Cell Journal of Pharmacology and Experimental Therapeutics
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH
QUICK SEARCH:   [advanced]


     

Plant Cell Advance Online Publication
Published on December 7, 2007; 10.1105/tpc.107.051508

This Article
Right arrow Full Text - TPC Advance Online Pub. (PDF)
Right arrow Supplemental Data
Right arrow All Versions of this Article:
19/12/3915    most recent
tpc.107.051508v1
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via CrossRef
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Khanna, R.
Right arrow Articles by Quail, P. H.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Khanna, R.
Right arrow Articles by Quail, P. H.
Agricola
Right arrow Articles by Khanna, R.
Right arrow Articles by Quail, P. H.

Received March 5, 2007
Returned for revision October 9, 2007
Accepted November 14, 2007

The Basic Helix-Loop-Helix Transcription Factor PIF5 Acts on Ethylene Biosynthesis and Phytochrome Signaling by Distinct Mechanisms

Rajnish Khanna 1, Yu Shen 1, Colleen M. Marion 1, Atsunari Tsuchisaka 1, Athanasios Theologis 1, Eberhard Schäfer 1, and Peter H. Quail 1*

1 Department of Plant and Microbial Biology, University of California, Berkeley, California 94720; U.S. Department of Agriculture/Agricultural Research Service, Plant Gene Expression Center, Albany, California 94710

* To whom correspondence should be addressed. E-mail: quail{at}nature.berkeley.edu.

PHYTOCHROME-INTERACTING FACTOR5 (PIF5), a basic helix-loop-helix transcription factor, interacts specifically with the photoactivated form of phytochrome B (phyB). Here, we report that dark-grown Arabidopsis thaliana seedlings overexpressing PIF5 (PIF5-OX) exhibit exaggerated apical hooks and short hypocotyls, reminiscent of the triple response induced by elevated ethylene levels, whereas pif5 mutants fail to maintain tight hooks like those of wild-type seedlings. Silver ions, an ethylene receptor blocker, rescued the triple-response phenotype, and we show that PIF5-OX seedlings express enhanced levels of key ethylene biosynthesis enzymes and produce elevated ethylene levels. Exposure of PIF5-OX seedlings to prolonged continuous red light (Rc) promotes hypocotyl elongation relative to dark controls, the reciprocal of the Rc-imposed hypocotyl inhibition displayed by wild-type seedlings. In contrast with this PIF5-OX hyposensitivity to Rc, pif5 mutant seedlings are hypersensitive relative to wild-type seedlings. We show that this contrast is due to reciprocal changes in phyB protein levels in prolonged Rc. Compared with wild-type seedlings, PIF5-OX seedlings have reduced, whereas pif5 mutants have increased, phyB (and phyC) levels in Rc. The phyB degradation in the overexpressors depends on a functional phyB binding motif in PIF5 and involves the 26S proteasome pathway. Our data thus indicate that overexpressed PIF5 causes altered ethylene levels, which promote the triple response in darkness, whereas in the light, the interaction of photoactivated phyB with PIF5 causes degradation of the photoreceptor protein. The evidence suggests that endogenous PIF5 negatively regulates phyB-imposed hypocotyl inhibition in prolonged Rc by reducing photoreceptor abundance, and thereby photosensory capacity, rather than functioning as a signaling intermediate.




This article has been cited by other articles:


Home page
 Proc. Natl. Acad. Sci. USAHome page
B. Al-Sady, E. A. Kikis, E. Monte, and P. H. Quail
Mechanistic duality of transcription factor function in phytochrome signaling
PNAS, February 12, 2008; 105(6): 2232 - 2237.
[Abstract] [Full Text] [PDF]


HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH
ASPB Publications THE PLANT CELL PLANT PHYSIOLOGY
Copyright © 2007 by the American Society of Plant Biologists