Missense mutation in the PAS2 domain of phytochrome A impairs subnuclear localization and a subset of responses.
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.
IFEVA, Facultad de Agronomía, Universidad de Buenos Aires, Av San Martín 4453, 1417-Buenos Aires, Argentina.
Marcelo J
MJ
Yanovsky
Juan Pablo
JP
Luppi
Daniel
D
Kirchbauer
Ouliana B
OB
Ogorodnikova
Vitally A
VA
Sineshchekov
Eva
E
Adam
Stefan
S
Kircher
Roberto J
RJ
Staneloni
Eberhard
E
Schäfer
Ferenc
F
Nagy
Jorge J
JJ
Casal
D000483:Alleles; D000872:Anthocyanins / Q000096:biosynthesis; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism / Q000528:radiation effects; D029681:Arabidopsis Proteins; D001665:Binding Sites / Q000235:genetics; D001692:Biological Transport / Q000528:radiation effects; D017124:Conserved Sequence / Q000235:genetics; D003624:Darkness; D005816:Genetic Complementation Test; D018525:Germination; D049452:Green Fluorescent Proteins; D018546:Hypocotyl / Q000254:growth & development; D008027:Light; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D008856:Microscopy, Fluorescence; D020125:Mutation, Missense / Q000235:genetics*; D009687:Nuclear Proteins / Q000235:genetics* / Q000378:metabolism / Q000528:radiation effects; D029543:Nucleocytoplasmic Transport Proteins / Q000235:genetics / Q000378:metabolism* / Q000528:radiation effects; D010786:Photoreceptor Cells; D010834:Phytochrome / Q000235:genetics* / Q000378:metabolism / Q000528:radiation effects; D051942:Phytochrome A; D051939:Phytochrome B; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism / Q000528:radiation effects; D012639:Seeds / Q000254:growth & development; D015398:Signal Transduction / Q000235:genetics / Q000528:radiation effects; D013997:Time Factors; D014157:Transcription Factors
D000872:Anthocyanins; D029681:Arabidopsis Proteins; D008164:Luminescent Proteins; D009687:Nuclear Proteins; D029543:Nucleocytoplasmic Transport Proteins; C497973:PHYA protein, Arabidopsis; C497952:PHYB protein, Arabidopsis; D051942:Phytochrome A; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; D010834:Phytochrome; D051939:Phytochrome B; D049452:Green Fluorescent Proteins