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Genes & Dev. 26 (8): 785-790

Copyright © 2012 by Cold Spring Harbor Laboratory Press.


Linking photoreceptor excitation to changes in plant architecture

Lin Li1,2, Karin Ljung3, Ghislain Breton4,7, Robert J. Schmitz5, Jose Pruneda-Paz4, Chris Cowing-Zitron6, Benjamin J. Cole1,2, Lauren J. Ivans1,8, Ullas V. Pedmale1,2, Hou-Sung Jung1,2, Joseph R. Ecker1,2,5, Steve A. Kay4,, and Joanne Chory1,2,9

1 Plant Biology Laboratory, The Salk Institute for Biological Studies, La Jolla, California 92037, USA;
2 Howard Hughes Medical Institute, The Salk Institute for Biological Studies, La Jolla, California 92037, USA;
3 Umeå Plant Science Centre, Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, SE-901 83 Umeå, Sweden;
4 Division of Biological Sciences, University of California at San Diego, La Jolla, California 92093, USA;
5 Genomic Analysis Laboratory, The Salk Institute for Biological Studies, La Jolla, California 92037, USA;
6 School of Medicine, University of California at San Diego, La Jolla, California 92093, USA

Abstract: Plants sense neighbor proximity as a decrease in the ratio of red to far-red light, which triggers a series of developmental responses. In Arabidopsis, phytochrome B (PHYB) is the major sensor of shade, but PHYB excitation has not been linked directly to a growth response. We show that the basic helix–loop–helix (bHLH) transcription factor PIF7 (phytochrome-interacting factor 7), an interactor of PHYB, accumulates in its dephosphorylated form in shade, allowing it to bind auxin biosynthetic genes and increase their expression. New auxin synthesized through a PIF7-regulated pathway is required for shade-induced growth, linking directly the perception of a light quality signal to a rapid growth response.

Key Words: auxin • phytochrome • shade avoidance

Received for publication January 21, 2012. Accepted for publication March 9, 2012.

7 Present addresses: Department of Integrative Biology and Pharmacology, The University of Texas Health Science Center at Houston, Houston, TX 77030, USA;

8 Department of Mathematics and Science Education, The University of Georgia, Athens, GA 30602, USA.

9 Corresponding author.

E-mail chory{at}

Supplemental material is available for this article.

Article is online at

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