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A short amino-terminal part of Arabidopsis phytochrome A induces constitutive photomorphogenic response

Viczián, András
Ádám, Éva
Wolf, Iris
Bindics, János
Kircher, Stefan
Schäfer, Eberhard
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Published in Molecular Plant. 2012, vol. 5, no. 3, p. 629-641
Abstract Phytochrome A (phyA) is the dominant photoreceptor of far-red light sensing in Arabidopsis thaliana. phyA accumulates at high levels in the cytoplasm of etiolated seedlings, and light-induced phyA signaling is mediated by a complex regulatory network. This includes light- and FHY1/FHL protein-dependent translocation of native phyA into the nucleus in vivo. It has also been shown that a short N-terminal fragment of phyA (PHYA406) is sufficient to phenocopy this highly regulated cellular process in vitro. To test the biological activity of this N-terminal fragment of phyA in planta, we produced transgenic phyA-201 plants expressing the PHYA406-YFP (YELLOW FLUORESCENT PROTEIN)-DD, PHYA406-YFP-DD-NLS (nuclear localization signal), and PHYA406-YFP-DD-NES (nuclear export signal) fusion proteins. Here, we report that PHYA406-YFP-DD is imported into the nucleus and this process is partially light-dependent whereas PHYA406-YFP-DD-NLS and PHYA406-YFP-DD-NES display the expected constitutive localization patterns. Our results show that these truncated phyA proteins are light-stable, they trigger a constitutive photomorphogenic-like response when localized in the nuclei, and neither of them induces proper phyA signaling. We demonstrate that in vitro and in vivo PHYA406 Pfr and Pr bind COP1, a general repressor of photomorphogenesis, and co-localize with it in nuclear bodies. Thus, we conclude that, in planta, the truncated PHYA406 proteins inactivate COP1 in the nuclei in a light-independent fashion.
Keywords Arabidopsis/genetics/growth & development/radiation effectsArabidopsis Proteins/chemistry/metabolismCell Nucleus/metabolism/radiation effectsHypocotyl/growth & development/radiation effectsIntracellular Space/metabolism/radiation effectsLightMorphogenesis/radiation effectsNuclear Localization Signals/metabolismPhenotypePhytochrome A/chemistry/metabolismPlants, Genetically ModifiedProtein Binding/radiation effectsProtein Transport/radiation effectsRecombinant Fusion Proteins/metabolismSeedling/growth & development/metabolism/radiation effectsStructure-Activity RelationshipUbiquitin-Protein Ligases/metabolism
PMID: 22498774
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VICZIÁN, András et al. A short amino-terminal part of Arabidopsis phytochrome A induces constitutive photomorphogenic response. In: Molecular Plant, 2012, vol. 5, n° 3, p. 629-641. https://archive-ouverte.unige.ch/unige:27987

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Deposited on : 2013-05-27

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