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BIOLOGICAL SCIENCES / PLANT BIOLOGY
Amino acid polymorphisms in Arabidopsis phytochrome B cause differential responses to light
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Section of Plant Biology, College of Biological Sciences, University of California, One Shields Avenue, Davis, CA 95616; Plant Biology Laboratory, and ¶Howard Hughes Medical Institute, Salk Institute for Biological Studies, La Jolla, CA 92037; ||Department of Ecology and Evolution, University of Chicago, Chicago, IL 60610; and Department of Molecular Biology, Max Planck Institute for Developmental Biology, 72076 Tübingen, Germany
Contributed by Joanne Chory, December 28, 2007 (received for review November 6, 2007)
Plants have a sophisticated system for sensing and responding to their light environment. The light responses of populations and species native to different habitats show adaptive variation; understanding the mechanisms underlying photomorphogenic variation is therefore of significant interest. In Arabidopsis thaliana, phytochrome B (PHYB) is the dominant photoreceptor for red light and plays a major role in white light. Because PHYB has been proposed as a candidate gene for several quantitative trait loci (QTLs) affecting light response, we have investigated sequence and functional variation in Arabidopsis PHYB. We examined PHYB sequences in 33 A. thaliana individuals and in the close relative Arabidopsis lyrata. From 14 nonsynonymous polymorphisms, we chose 5 for further study based on previous QTL studies. In a larger collection of A. thaliana accessions, one of these five polymorphisms, I143L, was associated with variation in red light response. We used transgenic analysis to test this association and confirmed experimentally that natural PHYB polymorphisms cause differential plant responses to light. Furthermore, our results show that allelic variation of PHYB activity is due to amino acid rather than regulatory changes. Together with earlier studies linking variation in light sensitivity to photoreceptor genes, our work suggests that photoreceptors may be a common target of natural selection.
hypocotyl | linkage disequilibrium | natural variation
Present Address: Department of Biology, Duke University, Box 90338, Durham, NC 27708.
The authors declare no conflict of interest.
Data Deposition: The sequences reported in this paper have been deposited in the GenBank database (accession nos. EU352775–EU352793).
This article contains supporting information online at www.pnas.org/cgi/content/full/0712174105/DC1.
To whom correspondence may be addressed. E-mail: chory{at}salk.edu or jnmaloof{at}ucdavis.edu
© 2008 by The National Academy of Sciences of the USA
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