title: The histidine kinase-related domain of Arabidopsis phytochrome a controls the spectral sensitivity and the subcellular distribution of the photoreceptor.
abstract: Phytochrome A (phyA) is the primary photoreceptor for sensing extremely low amounts of light and for mediating various far-red light-induced responses in higher plants. Translocation from the cytosol to the nucleus is an essential step in phyA signal transduction. EID1 (for EMPFINDLICHER IM DUNKELROTEN LICHT1) is an F-box protein that functions as a negative regulator in far-red light signaling downstream of the phyA in Arabidopsis (Arabidopsis thaliana). To identify factors involved in EID1-dependent light signal transduction, pools of ethylmethylsulfonate-treated eid1-3 seeds were screened for seedlings that suppress the hypersensitive phenotype of the mutant. The phenotype of the suppressor mutant presented here is caused by a missense mutation in the PHYA gene that leads to an amino acid transition in its histidine kinase-related domain. The novel phyA-402 allele alters the spectral sensitivity and the persistence of far-red light-induced high-irradiance responses. The strong eid1-3 suppressor phenotype of phyA-402 contrasts with the moderate phenotype observed when phyA-402 is introgressed into the wild-type background, which indicates that the mutation mainly alters functions in an EID1-dependent signaling cascade. The mutation specifically inhibits nuclear accumulation of the photoreceptor molecule upon red light irradiation, even though it still interacts with FHY1 (for far-red long hypocotyl 1) and FHL (for FHY1-like protein), two factors that are essential for nuclear accumulation of phyA. Degradation of the mutated phyA is unaltered even under light conditions that inhibit its nuclear accumulation, indicating that phyA degradation may occur mostly in the cytoplasm.
authors.affiliation: Albert-Ludwigs-Universität Freiburg, Institut für Biologie 2/Botanik, 79104 Freiburg, Germany.
authors.forename: Rebecca
authors.initials: R
authors.lastname: Müller
authors.forename: Aurora Piñas
authors.initials: AP
authors.lastname: Fernández
authors.forename: Andreas
authors.initials: A
authors.lastname: Hiltbrunner
authors.forename: Eberhard
authors.initials: E
authors.lastname: Schäfer
authors.forename: Thomas
authors.initials: T
authors.lastname: Kretsch
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism* / Q000528:radiation effects; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D001665:Binding Sites; D002467:Cell Nucleus / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D000071677:Histidine Kinase; D008027:Light; D008969:Molecular Sequence Data; D020125:Mutation, Missense; D010641:Phenotype; D010834:Phytochrome / Q000378:metabolism; D051942:Phytochrome A / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D011494:Protein Kinases / Q000378:metabolism; D021382:Protein Sorting Signals; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment; D015398:Signal Transduction; D014157:Transcription Factors / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; C524723:FHL protein, Arabidopsis; C441269:FHY1 protein, Arabidopsis; C497973:PHYA protein, Arabidopsis; D051942:Phytochrome A; D021382:Protein Sorting Signals; D014157:Transcription Factors; D010834:Phytochrome; D011494:Protein Kinases; D000071677:Histidine Kinase