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Missense Mutation in the PAS2 Domain of Phytochrome A Impairs Subnuclear Localization and a Subset of Responses

By Marcelo J. Yanovsky, Juan Pablo Luppi, Daniel Kirchbauer, Ouliana B. Ogorodnikova, Vitally A. Sineshchekov, Eva Adam, Stefan Kircher, Roberto J. Staneloni, Eberhard Schäfer, Ferenc Nagy and Jorge J. Casal

Abstract

Phytochrome A signaling shows two photobiologically discrete outputs: so-called very-low-fluence responses (VLFR) and high-irradiance responses (HIR). By modifying previous screening protocols, we isolated two Arabidopsis mutants retaining VLFR and lacking HIR. Phytochrome A negatively or positively regulates phytochrome B signaling, depending on light conditions. These mutants retained the negative but lacked the positive regulation. Both mutants carry the novel phyA-302 allele, in which Glu-777 (a residue conserved in angiosperm phytochromes) changed to Lys in the PAS2 motif of the C-terminal domain. The phyA-302 mutants showed a 50% reduction in phytochrome A levels in darkness, but this difference was compensated for by greater stability under continuous far-red light. phyA-302:green fluorescent protein fusion proteins showed normal translocation from the cytosol to the nucleus under continuous far-red light but failed to produce nuclear spots, suggesting that nuclear speckles could be involved in HIR signaling and phytochrome A degradation. We propose that the PAS2 domain of phytochrome A is necessary to initiate signaling in HIR but not in VLFR, likely via interaction with a specific partner

Topics: Research Article
Publisher: American Society of Plant Biologists
Year: 2002
DOI identifier: 10.1105/tpc.000521
OAI identifier: oai:pubmedcentral.nih.gov:150709
Provided by: PubMed Central
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