Chromophore-bearing NH₂-terminal domains of phytochromes A and B determine their photosensory specificity and differential light lability
Abstract
In early seedling development, far-red-light-induced deetiolation is mediated primarily by phytochrome A (phyA), whereas red-light-induced deetiolation is mediated primarily by phytochrome B (phyB). To map the molecular determinants responsible for this photosensory specificity, we tested the activities of two reciprocal phyA/phyB chimeras in diagnostic light regimes using overexpression in transgenic Arabidopsis. Although previous data have shown that the NH₂-terminal halves of phyA and phyB each separately lack normal activity, fusion of the NH₂-terminal half of phyA to the COOH-terminal half of phyB (phyAB) and the reciprocal fusion (phyBA) resulted in biologically active phytochromes. The behavior of these two chimeras in red and far-red light indicates: (i) that the NH₂-terminal halves of phyA and phyB determine their respective photosensory specificities; (ii) that the COOH-terminal halves of the two photoreceptors are necessary for regulatory activity but are reciprocally inter-changeable and thus carry functionally equivalent determinants; and (iii) that the NH₂-terminal halves of phyA and phyB carry determinants that direct the differential light lability of the two molecules. The present findings suggest that the contrasting photosensory information gathered by phyA and phyB through their NH₂-terminal halves may be transduced to downstream signaling components through a common biochemical mechanism involving the regulatory activity of the COOH-terminal domains of the photoreceptors.
Additional Information
© 1996 National Academy of Sciences. Communicated by Winslow R. Briggs, Carnegie Institution of Washington, Stanford, CA, December 27, 1995 (received for review August 10, 1995). We thank John Wagner and David Dailey for critical reading of the manuscript and valuable suggestions, Yong Xu for useful discussion, Jim Tepperman for help with the antibody production, and David Hantz and the greenhouse staff for expert care of our plants. This research was supported by grants from the Cancer Research Fund of the Damon Runyon-Walter Winchell Foundation (Fellowship DRG-1302 to C.F.) and by Department of Energy Grant FG03-92ER13742, National Institutes of Health Grant GM47475, and U.S. Department of Agriculture Agricultural Research Service Current Research Information Service Grant 5335-21000-006-00D (to P.H.Q.). The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.Attached Files
Published - PNAS-1996-Wagner-4011-5.pdf
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Additional details
- PMCID
- PMC39477
- Eprint ID
- 52343
- Resolver ID
- CaltechAUTHORS:20141203-134442711
- DRG-1302
- Damon Runyon-Walter Winchell Foundation
- FG03-92ER13742
- Department of Energy (DOE)
- GM47475
- NIH
- 5335-21000-006-00D
- U.S. Department of Agriculture
- Created
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2014-12-04Created from EPrint's datestamp field
- Updated
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2023-06-06Created from EPrint's last_modified field