Arabidopsis thaliana HY1 locus, required for phytochrome-chromophore biosynthesis, encodes a protein related to heme oxygenases

• Published in: Proceedings of the National Academy of Sciences - PNAS 1999-05, Vol.96 (11), p.6541-6546
• Main Authors: Davis, S.J, Kurepa, J, Vierstra, R.D
• Format: Article
• Language: English
• Subjects: Alleles; Amino Acid Sequence; amino acid sequences; Animals; Arabidopsis - genetics; Arabidopsis - growth & development; Arabidopsis - metabolism; Arabidopsis thaliana; Base Sequence; Biliverdine - metabolism; Biological Sciences; Biology; chromosome mapping; Cloning; Cloning, Molecular; Codon, Terminator; complementary DNA; Cyanobacteria - enzymology; Cyanobacteria - genetics; DNA Primers; Eukaryota - enzymology; Eukaryota - genetics; Flowers & plants; genbank/af132475; genbank/af132476; genbank/af132477; gene expression; Genes, Plant; genetic complementation; Genetic Complementation Test; Genetic loci; Genetic mutation; Genetic vectors; Genomics; Heme Oxygenase (Decyclizing) - chemistry; Heme Oxygenase (Decyclizing) - metabolism; Humans; hypocotyls; loci; Messenger RNA; Molecular Sequence Data; Multigene Family; Mutagenesis; mutants; Mutation; nucleotide sequences; open reading frames; oxygenases; phenotype; Phytochrome - biosynthesis; Plant cells; Plants; Proteins; RNA; seedling growth; Seedlings; Sequence Alignment; Sequence Homology, Amino Acid; transgenic plants
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.96.11.6541

The hy1 mutants of Arabidopsis thaliana fail to make the phytochrome-chromophore phytochromobilin and therefore are deficient in a wide range of phytochrome-mediated responses. Because this defect can be rescued by feeding seedlings biliverdin IX alpha, it is likely that the mutations affect an enzyme that converts heme to this phytochromobilin intermediate. By a combination of positional cloning and candidate-gene isolation, we have identified the HY1 gene and found it to be related to cyanobacterial, algal, and animal heme oxygenases. Three independent alleles of hy1 contain DNA lesions within the HY1 coding region, and a genomic sequence spanning the Hy1 locus complements the hy1-1 mutation. HY1 is a member of a gene family and is expressed in a variety of A. thaliana tissues. Based on its homology, we propose that HY1 encodes a higher-plant heme oxygenase, designated AtHO1, responsible for catalyzing the reaction that opens the tetrapyrrole ring of heme to generate biliverdin IX alpha.