AUREOCHROME, a photoreceptor required for photomorphogenesis in stramenopiles.
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 approximately 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.
Takahashi
Fumio
F
Division of Biological Regulation and Photobiology, National Institute for Basic Biology, Okazaki 444-8585, Japan.
Yamagata
Daisuke
D
Ishikawa
Mié
M
Fukamatsu
Yosuke
Y
Ogura
Yasunobu
Y
Kasahara
Masahiro
M
Kiyosue
Tomohiro
T
Kikuyama
Munehiro
M
Wada
Masamitsu
M
Kataoka
Hironao
H
D000595:Amino Acid Sequence; D017377:Diatoms / Q000235:genetics / Q000254:growth & development*; D044645:Fucus / Q000235:genetics / Q000254:growth & development*; D005786:Gene Expression Regulation; D008969:Molecular Sequence Data; D009024:Morphogenesis / Q000235:genetics; D000459:Phaeophyceae / Q000235:genetics / Q000254:growth & development*; D010786:Photoreceptor Cells / Q000737:chemistry / Q000187:drug effects / Q000502:physiology*; D017434:Protein Structure, Tertiary; D034622:RNA Interference; D014158:Transcription, Genetic