LAF1, a MYB transcription activator for phytochrome A signaling.
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).
Ballesteros
M L
ML
Laboratory of Plant Molecular Biology, The Rockefeller University, New York, NY 10021-6399, USA.
Bolle
C
C
Lois
L M
LM
Moore
J M
JM
Vielle-Calzada
J P
JP
Grossniklaus
U
U
Chua
N H
NH
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
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