AUREOCHROME, a photoreceptor required for photomorphogenesis in stramenopiles

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 104; no. 49; pp. 19625 - 19630
• Main Authors: Takahashi, Fumio, Yamagata, Daisuke, Ishikawa, Mié, Fukamatsu, Yosuke, Ogura, Yasunobu, Kasahara, Masahiro, Kiyosue, Tomohiro, Kikuyama, Munehiro, Wada, Masamitsu, Kataoka, Hironao
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 04.12.2007; National Acad Sciences
• Subjects: Algae; Amino Acid Sequence; AUREOCHROME proteins; Bacillariophyceae; Binding sites; Biological Sciences; blue light; blue light receptors; cell differentiation; chromoproteins; Diatoms - genetics; Diatoms - growth & development; DNA; Double stranded RNA; Eukaryotes; Fluorescence; Fucus - genetics; Fucus - growth & development; Fucus distichus; Gene Expression Regulation; Genomes; Genomics; Irradiation; Molecular Sequence Data; morphogenesis; Morphogenesis - genetics; Phaeophyceae; Phaeophyceae - genetics; Phaeophyceae - growth & development; photomorphogenesis; Photoreceptor Cells - chemistry; Photoreceptor Cells - drug effects; Photoreceptor Cells - physiology; Photoreceptors; Phototropism; Plant cells; Plants; Protein Structure, Tertiary; protein-protein interactions; Proteins; Receptors; Ribonucleic acid; RNA; RNA Interference; Stramenopiles; Thalassiosira; Thalassiosira pseudonana; transcription factors; Transcription, Genetic; Vaucheria; Vaucheria frigida; Xanthophyceae
• ISSN: 0027-8424; 1091-6490; 1091-6490
• DOI: 10.1073/pnas.0707692104

A blue light (BL) receptor was discovered in stramenopile algae Vaucheria frigida (Xanthophyceae) and Fucus distichus (Phaeophyceae). Two homologs were identified in Vaucheria; each has one basic region/leucine zipper (bZIP) domain and one light-oxygen-voltage (LOV)-sensing domain. We named these chromoproteins AUREOCHROMEs (AUREO1 and AUREO2). AUREO1 binds flavin mononucleotide via its LOV domain and forms a 390-nm-absorbing form, indicative of formation of a cysteinyl adduct to the C(4a) carbon of the flavin mononucleotide upon BL irradiation. The adduct decays to the ground state in [almost equal to]5 min. Its bZIP domain binds the target sequence TGACGT. The AUREO1 target binding was strongly enhanced by BL treatment, implying that AUREO1 functions as a BL-regulated transcription factor. The function of AUREO1 as photoreceptor for BL-induced branching is elucidated through RNAi experiments. RNAi of AUREO2 unexpectedly induces sex organ primordia instead of branches, implicating AUREO2 as a subswitch to initiate development of a branch, but not a sex organ. AUREO sequences are also found in the genome of the marine diatom Thalassiosira pseudonana (Bacillariophyceae), but are not present in green plants. AUREOCHROME therefore represents a BL receptor in photosynthetic stramenopiles.