title: LAF1, a MYB transcription activator for phytochrome A signaling.
abstract: The photoreceptor phytochrome (phy) A has a well-defined role in regulating gene expression in response to specific light signals. Here, we describe a new Arabidopsis mutant, laf1 (long after far-red light 1) that has an elongated hypocotyl specifically under far-red light. Gene expression studies showed that laf1 has reduced responsiveness to continuous far-red light but retains wild-type responses to other light wavelengths. As far-red light is only perceived by phyA, our results suggest that LAF1 is specifically involved in phyA signal transduction. Further analyses revealed that laf1 is affected in a subset of phyA-dependent responses and the phenotype is more severe at low far-red fluence rates. LAF1 encodes a nuclear protein with strong homology with the R2R3-MYB family of DNA-binding proteins. Experiments using yeast cells identified a transactivation domain in the C-terminal portion of the protein. LAF1 is constitutively targeted to the nucleus by signals in its N-terminal portion, and the full-length protein accumulates in distinct nuclear speckles. This accumulation in speckles is abolished by a point mutation in a lysine residue (K258R), which might serve as a modification site by a small ubiquitin-like protein (SUMO).
authors.affiliation: Laboratory of Plant Molecular Biology, The Rockefeller University, New York, NY 10021-6399, USA.
authors.forename: M L
authors.initials: ML
authors.lastname: Ballesteros
authors.forename: C
authors.initials: C
authors.lastname: Bolle
authors.forename: L M
authors.initials: LM
authors.lastname: Lois
authors.forename: J M
authors.initials: JM
authors.lastname: Moore
authors.forename: J P
authors.initials: JP
authors.lastname: Vielle-Calzada
authors.forename: U
authors.initials: U
authors.lastname: Grossniklaus
authors.forename: N H
authors.initials: NH
authors.lastname: Chua
mesh_terms: D000595:Amino Acid Sequence; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D002467:Cell Nucleus / Q000378:metabolism; D003001:Cloning, Molecular; D017931:DNA Primers; D006034:Glycyrrhetinic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D049452:Green Fluorescent Proteins; D008164:Luminescent Proteins / Q000235:genetics; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D010834:Phytochrome / Q000378:metabolism*; D051942:Phytochrome A; D017354:Point Mutation; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction / Q000502:physiology*; D015534:Trans-Activators / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D017931:DNA Primers; C438763:LAF1 protein, Arabidopsis; D008164:Luminescent Proteins; D009687:Nuclear Proteins; C497973:PHYA protein, Arabidopsis; D051942:Phytochrome A; D011993:Recombinant Fusion Proteins; D015534:Trans-Activators; D010834:Phytochrome; D049452:Green Fluorescent Proteins; D006034:Glycyrrhetinic Acid