title: HY4 gene of A. thaliana encodes a protein with characteristics of a blue-light photoreceptor.
abstract: Specific responses to blue light are found throughout the biological kingdom. These responses--which in higher plants include phototropism, inhibition of hypocotyl elongation, and stomatal opening--are in many cases thought to be mediated by flavin-type photoreceptors. But no such blue-light photoreceptor has yet been identified or isolated, although blue-light responses in plants were reported by Darwin over a century ago, long before the discovery of the now relatively well characterized red/far-red light photoreceptor, phytochrome. Here we describe the isolation of a gene corresponding to the HY4 locus of Arabidopsis thaliana. The hy4 mutant is one of several mutants that are selectively insensitive to blue light during the blue-light-dependent inhibition of hypocotyl elongation response, which suggests that they lack an essential component of the cryptochrome-associated light-sensing pathway. The HY4 gene, isolated by gene tagging, was shown to encode a protein with significant homology to microbial DNA photolyases. As photolyases are a rare class of flavoprotein that catalyse blue-light-dependent reactions, the protein encoded by HY4 has a structure consistent with that of a flavin-type blue-light photoreceptor.
authors.affiliation: Department of Biology, University of Pennsylvania, Philadelphia 19104.
authors.forename: M
authors.initials: M
authors.lastname: Ahmad
authors.forename: A R
authors.initials: AR
authors.lastname: Cashmore
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis; D029681:Arabidopsis Proteins; D001483:Base Sequence; D056931:Cryptochromes; D004255:Deoxyribodipyrimidine Photo-Lyase / Q000235:genetics; D029721:Drosophila Proteins; D005136:Eye Proteins; D005420:Flavoproteins; D017343:Genes, Plant; D008027:Light; D008969:Molecular Sequence Data; D009154:Mutation; D010786:Photoreceptor Cells; D017956:Photoreceptor Cells, Invertebrate; D010940:Plant Proteins / Q000235:genetics*; D043562:Receptors, G-Protein-Coupled; D017386:Sequence Homology, Amino Acid
chemical_list: D029681:Arabidopsis Proteins; C538962:CRY1 protein, Arabidopsis; D056931:Cryptochromes; D029721:Drosophila Proteins; D005136:Eye Proteins; D005420:Flavoproteins; D010940:Plant Proteins; D043562:Receptors, G-Protein-Coupled; C119828:cry protein, Drosophila; D004255:Deoxyribodipyrimidine Photo-Lyase