title: Nuclear translocation of the photoreceptor phytochrome B is necessary for its biological function in seedling photomorphogenesis.
abstract: The phytochrome (phy) family of sensory photoreceptors (phyA to phyE in Arabidopsis) enables plants to optimize their growth and development under natural light environments. Subcellular localization studies have shown that the photoreceptor molecule is induced to translocate from cytosol to nucleus by light, but direct evidence of the functional relevance of this translocation has been lacking. Here, using a glucocorticoid receptor-based fusion protein system, we demonstrate that both photoactivation and nuclear translocation combined are necessary and sufficient for the biological function of phyB. Conversely, neither artificial nuclear translocation of non-photoactivated phyB nor artificial retention of photoactivated phyB in the cytosol provides detectable biological activity. Together these data indicate that signal transfer from photoactivated phyB to its primary signaling partner(s) is localized in the nucleus, and conversely suggest the absence of a cytosolic pathway from photoactivated phyB to light-responsive genes.
authors.affiliation: Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720, USA.
authors.forename: Enamul
authors.initials: E
authors.lastname: Huq
authors.forename: Bassem
authors.initials: B
authors.lastname: Al-Sady
authors.forename: Peter H
authors.initials: PH
authors.lastname: Quail
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000502:physiology* / Q000528:radiation effects; D029681:Arabidopsis Proteins; D002467:Cell Nucleus / Q000502:physiology / Q000528:radiation effects; D003600:Cytosol / Q000502:physiology / Q000528:radiation effects; D008027:Light; D010786:Photoreceptor Cells; D045322:Photosynthetic Reaction Center Complex Proteins / Q000235:genetics / Q000502:physiology*; D010834:Phytochrome / Q000235:genetics / Q000502:physiology*; D051939:Phytochrome B; D030821:Plants, Genetically Modified; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology* / Q000528:radiation effects; D014157:Transcription Factors
chemical_list: D029681:Arabidopsis Proteins; C497952:PHYB protein, Arabidopsis; D045322:Photosynthetic Reaction Center Complex Proteins; D014157:Transcription Factors; D010834:Phytochrome; D051939:Phytochrome B