title: Hd1,a CONSTANS ortholog in rice, functions as an Ehd1 repressor through interaction with monocot-specific CCT-domain protein Ghd7.
abstract: Flowering time is an important agronomic trait that affects crop yields. In cereals, several CCT-domain proteins unique to monocots, such as Grain number, plant height, and heading date 7 (Ghd7) gene, have been identified as key floral repressors, although the corresponding molecular mechanisms have been unknown until now. In rice, a short-day plant, Heading date 1 (Hd1) gene, a rice ortholog of Arabidopsis floral activator CONSTANS (CO), represses flowering under non-inductive long-day (LD) conditions and induces it under inductive short-day (SD) conditions. Here, we report biological interactions between Ghd7 and Hd1, which together repress Early heading date 1 (Ehd1), a key floral inducer under non-inductive LD conditions. In addition to this genetic interaction between them, Co-IP experiments further demonstrated that a Ghd7-Hd1 protein formed a complex in vivo and ChIP and luciferase reporter analyses suggested that this complex specifically binds to a cis-regulatory region in Ehd1 and represses its expression. These findings imply that Hd1, an evolutionally conserved transcriptional activator, can function as a strong transcriptional repressor within a monocot-specific flowering-time pathway through with Ghd7.
authors.affiliation: Functional Plant Research Unit, National Institute of Agrobiological Sciences, Kannondai, Tsukuba, Ibaraki, 305-8602, Japan.
authors.forename: Yasue
authors.initials: Y
authors.lastname: Nemoto
authors.affiliation: Agrogenomics Research Center, National Institute of Agrobiological Sciences, Kannondai, Tsukuba, Ibaraki, 305-8602, Japan.
authors.forename: Yasunori
authors.initials: Y
authors.lastname: Nonoue
authors.affiliation: Functional Plant Research Unit, National Institute of Agrobiological Sciences, Kannondai, Tsukuba, Ibaraki, 305-8602, Japan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Yano
authors.affiliation: Department of Molecular Genetics, National Institute of Agrobiological Sciences, Kannondai, Tsukuba, Ibaraki, 305-8602, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Izawa
mesh_terms: D015536:Down-Regulation; D035264:Flowers / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D012275:Oryza / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D000072417:Protein Domains; D012333:RNA, Messenger / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism / Q000502:physiology*
chemical_list: D010940:Plant Proteins; D012333:RNA, Messenger; D014157:Transcription Factors
keywords: flowering time; monocot-specific pathway; repressor complex; rice