Residues clustered in the light-sensing knot of phytochrome B are necessary for conformer-specific binding to signaling partner PIF3.

The bHLH transcription factor, Phytochrome Interacting Factor 3 (PIF3), interacts specifically with the photoactivated, Pfr, form of Arabidopsis phytochrome B (phyB). This interaction induces PIF3 phosphorylation and degradation in vivo and modulates phyB-mediated seedling deetiolation in response t...

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Main Authors: Elise A Kikis, Yoshito Oka, Matthew E Hudson, Akira Nagatani, Peter H Quail
Format: Article
Language:English
Published: Public Library of Science (PLoS) 2009-01-01
Series:PLoS Genetics
Online Access:http://europepmc.org/articles/PMC2621353?pdf=render
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spelling doaj-a505c4dec62f4b7da971b967b2c3ddab2020-11-25T00:53:43ZengPublic Library of Science (PLoS)PLoS Genetics1553-73901553-74042009-01-0151e100035210.1371/journal.pgen.1000352Residues clustered in the light-sensing knot of phytochrome B are necessary for conformer-specific binding to signaling partner PIF3.Elise A KikisYoshito OkaMatthew E HudsonAkira NagataniPeter H QuailThe bHLH transcription factor, Phytochrome Interacting Factor 3 (PIF3), interacts specifically with the photoactivated, Pfr, form of Arabidopsis phytochrome B (phyB). This interaction induces PIF3 phosphorylation and degradation in vivo and modulates phyB-mediated seedling deetiolation in response to red light. To identify missense mutations in the phyB N-terminal domain that disrupt this interaction, we developed a yeast reverse-hybrid screen. Fifteen individual mutations identified in this screen, or in previous genetic screens for Arabidopsis mutants showing reduced sensitivity to red light, were shown to also disrupt light-induced binding of phyB to PIF3 in in vitro co-immunoprecipitation assays. These phyB missense mutants fall into two general classes: Class I (eleven mutants) containing those defective in light signal perception, due to aberrant chromophore attachment or photoconversion, and Class II (four mutants) containing those normal in signal perception, but defective in the capacity to transduce this signal to PIF3. By generating a homology model for the three-dimensional structure of the Arabidopsis phyB chromophore-binding region, based on the crystal structure of Deinococcus radiodurans phytochrome, we predict that three of the four Class II mutated phyB residues are solvent exposed in a cleft between the presumptive PAS and GAF domains. This deduction suggests that these residues could be directly required for the physical interaction of phyB with PIF3. Because these three residues are also necessary for phyB-imposed inhibition of hypocotyl elongation in response to red light, they are functionally necessary for signal transfer from photoactivated phyB, not only to PIF3 and other related bHLH transcription factors tested here, but also to other downstream signaling components involved in regulating seedling deetiolation.http://europepmc.org/articles/PMC2621353?pdf=render
collection DOAJ
language English
format Article
sources DOAJ
author Elise A Kikis
Yoshito Oka
Matthew E Hudson
Akira Nagatani
Peter H Quail
spellingShingle Elise A Kikis
Yoshito Oka
Matthew E Hudson
Akira Nagatani
Peter H Quail
Residues clustered in the light-sensing knot of phytochrome B are necessary for conformer-specific binding to signaling partner PIF3.
PLoS Genetics
author_facet Elise A Kikis
Yoshito Oka
Matthew E Hudson
Akira Nagatani
Peter H Quail
author_sort Elise A Kikis
title Residues clustered in the light-sensing knot of phytochrome B are necessary for conformer-specific binding to signaling partner PIF3.
title_short Residues clustered in the light-sensing knot of phytochrome B are necessary for conformer-specific binding to signaling partner PIF3.
title_full Residues clustered in the light-sensing knot of phytochrome B are necessary for conformer-specific binding to signaling partner PIF3.
title_fullStr Residues clustered in the light-sensing knot of phytochrome B are necessary for conformer-specific binding to signaling partner PIF3.
title_full_unstemmed Residues clustered in the light-sensing knot of phytochrome B are necessary for conformer-specific binding to signaling partner PIF3.
title_sort residues clustered in the light-sensing knot of phytochrome b are necessary for conformer-specific binding to signaling partner pif3.
publisher Public Library of Science (PLoS)
series PLoS Genetics
issn 1553-7390
1553-7404
publishDate 2009-01-01
description The bHLH transcription factor, Phytochrome Interacting Factor 3 (PIF3), interacts specifically with the photoactivated, Pfr, form of Arabidopsis phytochrome B (phyB). This interaction induces PIF3 phosphorylation and degradation in vivo and modulates phyB-mediated seedling deetiolation in response to red light. To identify missense mutations in the phyB N-terminal domain that disrupt this interaction, we developed a yeast reverse-hybrid screen. Fifteen individual mutations identified in this screen, or in previous genetic screens for Arabidopsis mutants showing reduced sensitivity to red light, were shown to also disrupt light-induced binding of phyB to PIF3 in in vitro co-immunoprecipitation assays. These phyB missense mutants fall into two general classes: Class I (eleven mutants) containing those defective in light signal perception, due to aberrant chromophore attachment or photoconversion, and Class II (four mutants) containing those normal in signal perception, but defective in the capacity to transduce this signal to PIF3. By generating a homology model for the three-dimensional structure of the Arabidopsis phyB chromophore-binding region, based on the crystal structure of Deinococcus radiodurans phytochrome, we predict that three of the four Class II mutated phyB residues are solvent exposed in a cleft between the presumptive PAS and GAF domains. This deduction suggests that these residues could be directly required for the physical interaction of phyB with PIF3. Because these three residues are also necessary for phyB-imposed inhibition of hypocotyl elongation in response to red light, they are functionally necessary for signal transfer from photoactivated phyB, not only to PIF3 and other related bHLH transcription factors tested here, but also to other downstream signaling components involved in regulating seedling deetiolation.
url http://europepmc.org/articles/PMC2621353?pdf=render
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