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 light1) 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 thatlaf1 is affected in a subset of phyA-dependent responses and the phenotype is more severe at low far-red fluence rates. LAF1encodes 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).
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Footnotes
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Present addresses: 4I.N.I.A., Departamento de Mejora Genética y Biotecnologı́a, Carretera de La Coruña km 7.5, 28040 Madrid, Spain; 5Institute of Plant Biology, University of Zürich, Zollikerstrasse 107, 8008 Zürich, Switzerland; 6Laboratory of Reproductive Development and Apomixis, CINVESTAV-Plant Biotechnology Unit, Km 96 Libramiento Norte Carr., 36500 Irapuato GTO, Mexico.
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↵7 These authors contributed equally to this work.
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↵8 Corresponding author.
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E-MAIL chua{at}rockvax.rockefeller.edu; FAX (212) 327-8327.
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Article and publication are at http://www.genesdev.org/cgi/doi/10.1101/gad.915001.
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- Received May 29, 2001.
- Accepted August 1, 2001.
- Cold Spring Harbor Laboratory Press
