title: Hd16, a gene for casein kinase I, is involved in the control of rice flowering time by modulating the day-length response.
abstract: The alteration of photoperiod sensitivity has let breeders diversify flowering time in Oryza sativa (rice) and develop cultivars adjusted to a range of growing season periods. Map-based cloning revealed that the rice flowering-time quantitative trait locus (QTL) Heading date 16 (Hd16) encodes a casein kinase-I protein. One non-synonymous substitution in Hd16 resulted in decreased photoperiod sensitivity in rice, and this substitution occurred naturally in an old rice cultivar. By using near-isogenic lines with functional or deficient alleles of several rice flowering-time genes, we observed significant digenetic interactions between Hd16 and four other flowering-time genes (Ghd7, Hd1, DTH8 and Hd2). In a near-isogenic line with the weak-photoperiod-sensitivity allele of Hd16, transcription levels of Ehd1, Hd3a, and RFT1 increased under long-day conditions, and transcription levels of Hd3a and RFT1 decreased under short-day conditions. Expression analysis under continuous light and dark conditions showed that Hd16 was not likely to be associated with circadian clock regulation. Biochemical characterization indicated that the functional Hd16 recombinant protein specifically phosphorylated Ghd7. These results demonstrate that Hd16 acts as an inhibitor in the rice flowering pathway by enhancing the photoperiod response as a result of the phosphorylation of Ghd7.
authors.affiliation: National Institute of Agrobiological Sciences, 2-1-2 Kannondai, Tsukuba, Ibaraki, 305-8602, Japan.
authors.forename: Kiyosumi
authors.initials: K
authors.lastname: Hori
authors.forename: Eri
authors.initials: E
authors.lastname: Ogiso-Tanaka
authors.forename: Kazuki
authors.initials: K
authors.lastname: Matsubara
authors.forename: Utako
authors.initials: U
authors.lastname: Yamanouchi
authors.forename: Kaworu
authors.initials: K
authors.lastname: Ebana
authors.forename: Masahiro
authors.initials: M
authors.lastname: Yano
mesh_terms: D000483:Alleles; D047389:Casein Kinase I / Q000235:genetics* / Q000378:metabolism; D002874:Chromosome Mapping; D002940:Circadian Rhythm; D035264:Flowers / Q000201:enzymology* / Q000235:genetics / Q000502:physiology / Q000528:radiation effects; D018506:Gene Expression Regulation, Plant; D008027:Light; D008958:Models, Molecular; D012275:Oryza / Q000201:enzymology* / Q000235:genetics / Q000502:physiology / Q000528:radiation effects; D010766:Phosphorylation; D017440:Photoperiod; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D020641:Polymorphism, Single Nucleotide; D040641:Quantitative Trait Loci / Q000235:genetics; D011994:Recombinant Proteins; D012621:Seasons; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D020798:Two-Hybrid System Techniques
chemical_list: D010940:Plant Proteins; D011994:Recombinant Proteins; D014157:Transcription Factors; D047389:Casein Kinase I
keywords: Oryza sativa L.; casein kinase I; flowering time; natural variation; photoperiod sensitivity