title: Suppression of the floral activator Hd3a is the principal cause of the night break effect in rice.
abstract: A short exposure to light in the middle of the night causes inhibition of flowering in short-day plants. This phenomenon is called night break (NB) and has been used extensively as a tool to study the photoperiodic control of flowering for many years. However, at the molecular level, very little is known about this phenomenon. In rice (Oryza sativa), 10 min of light exposure in the middle of a 14-h night caused a clear delay in flowering. A single NB strongly suppressed the mRNA of Hd3a, a homolog of Arabidopsis thaliana FLOWERING LOCUS T (FT), whereas the mRNAs of OsGI and Hd1 were not affected. The NB effect on Hd3a mRNA was maximal in the middle of the 14-h night. The phyB mutation abolished the NB effect on flowering and Hd3a mRNA, indicating that the NB effect was mediated by phytochrome B. Because expression of the other FT-like genes was very low and not appreciably affected by NB, our results strongly suggest that the suppression of Hd3a mRNA is the principal cause of the NB effect on flowering in rice.
authors.affiliation: Laboratory of Plant Molecular Genetics, Nara Institute of Science and Technology, Takayama, Ikoma, Japan.
authors.forename: Ryo
authors.initials: R
authors.lastname: Ishikawa
authors.forename: Shojiro
authors.initials: S
authors.lastname: Tamaki
authors.forename: Shuji
authors.initials: S
authors.lastname: Yokoi
authors.forename: Noritoshi
authors.initials: N
authors.lastname: Inagaki
authors.forename: Tomoko
authors.initials: T
authors.lastname: Shinomura
authors.forename: Makoto
authors.initials: M
authors.lastname: Takano
authors.forename: Ko
authors.initials: K
authors.lastname: Shimamoto
mesh_terms: D008969:Molecular Sequence Data; D012275:Oryza / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D051939:Phytochrome B / Q000502:physiology; D010940:Plant Proteins / Q000235:genetics / Q000502:physiology*; D030821:Plants, Genetically Modified / Q000235:genetics / Q000502:physiology; D012333:RNA, Messenger / Q000235:genetics; D014158:Transcription, Genetic
chemical_list: D010940:Plant Proteins; D012333:RNA, Messenger; D051939:Phytochrome B