An Arabidopsis mutant hypersensitive to red and far-red light signals.
A new mutant called psi2 (for phytochrome signaling) was isolated by screening for elevated activity of a chlorophyll a/b binding protein-luciferase (CAB2-LUC) transgene in Arabidopsis. This mutant exhibited hypersensitive induction of CAB1, CAB2, and the small subunit of ribulose-1,5-bisphosphate carboxylase (RBCS) promoters in the very low fluence range of red light and a hypersensitive response in hypocotyl growth in continuous red light of higher fluences. In addition, at high- but not low-light fluence rates, the mutant showed light-dependent superinduction of the pathogen-related protein gene PR-1a and developed spontaneous necrotic lesions in the absence of any pathogen. Expression of genes responding to various hormone and environmental stress pathways in the mutant was not significantly different from that of the wild type. Analysis of double mutants demonstrated that the effects of the psi2 mutation are dependent on both phytochromes phyA and phyB. The mutation is recessive and maps to the bottom of chromosome 5. Together, our results suggest that PSI2 specifically and negatively regulates both phyA and phyB phototransduction pathways. The induction of cell death by deregulated signaling pathways observed in psi2 is reminiscent of retinal degenerative diseases in animals and humans.
Genoud
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Laboratory of Plant Molecular Biology, The Rockefeller University, 1230 York Avenue, New York, New York 10021-6399, USA.
Millar
A J
AJ
Nishizawa
N
N
Kay
S A
SA
Schäfer
E
E
Nagatani
A
A
Chua
N H
NH
D017360:Arabidopsis / Q000235:genetics / Q000502:physiology* / Q000528:radiation effects; D029681:Arabidopsis Proteins; D001483:Base Sequence; D002352:Carrier Proteins / Q000096:biosynthesis / Q000235:genetics*; D002874:Chromosome Mapping; D018506:Gene Expression Regulation, Plant / Q000528:radiation effects; D017343:Genes, Plant; D005808:Genes, Recessive; D008027:Light; D045342:Light-Harvesting Protein Complexes; D008029:Lighting; D008156:Luciferases / Q000096:biosynthesis / Q000235:genetics; D008969:Molecular Sequence Data; D016296:Mutagenesis; D009838:Oligodeoxyribonucleotides; D010786:Photoreceptor Cells; D045322:Photosynthetic Reaction Center Complex Proteins / Q000096:biosynthesis / Q000235:genetics; D010834:Phytochrome / Q000378:metabolism; D051942:Phytochrome A; D051939:Phytochrome B; D018515:Plant Leaves; D010940:Plant Proteins / Q000096:biosynthesis / Q000235:genetics*; D030821:Plants, Genetically Modified; D018087:Plastids; D012273:Ribulose-Bisphosphate Carboxylase / Q000096:biosynthesis / Q000235:genetics; D014157:Transcription Factors; D014158:Transcription, Genetic
D029681:Arabidopsis Proteins; D002352:Carrier Proteins; D045342:Light-Harvesting Protein Complexes; D009838:Oligodeoxyribonucleotides; C497973:PHYA protein, Arabidopsis; C497952:PHYB protein, Arabidopsis; D045322:Photosynthetic Reaction Center Complex Proteins; D051942:Phytochrome A; D010940:Plant Proteins; D014157:Transcription Factors; D010834:Phytochrome; D051939:Phytochrome B; D008156:Luciferases; D012273:Ribulose-Bisphosphate Carboxylase