title: OsCOL4 is a constitutive flowering repressor upstream of Ehd1 and downstream of OsphyB.
abstract: Plants recognize environmental factors to determine flowering time. CONSTANS (CO) plays a central role in the photoperiod flowering pathway of Arabidopsis, and CO protein stability is modulated by photoreceptors. In rice, Hd1, an ortholog of CO, acts as a flowering promoter, and phytochromes repress Hd1 expression. Here, we investigated the functioning of OsCOL4, a member of the CONSTANS-like (COL) family in rice. OsCOL4 null mutants flowered early under short or long days. In contrast, OsCOL4 activation-tagging mutants (OsCOL4-D) flowered late in either environment. Transcripts of Ehd1, Hd3a, and RFT1 were increased in the oscol4 mutants, but reduced in the OsCOL4-D mutants. This finding indicates that OsCOL4 is a constitutive repressor functioning upstream of Ehd1. By comparison, levels of Hd1, OsID1, OsMADS50, OsMADS51, and OsMADS56 transcripts were not significantly changed in oscol4 or OsCOL4-D, suggesting that OsCOL4 functions independently from previously reported flowering pathways. In osphyB mutants, OsCOL4 expression was decreased and osphyB oscol4 double mutants flowered at the same time as the osphyB single mutants, indicating OsCOL4 functions downstream of OsphyB. We also present evidence for two independent pathways through which OsPhyB controls flowering time. These pathways are: (i) night break-sensitive, which does not need OsCOL4; and (ii) night break-insensitive, in which OsCOL4 functions between OsphyB and Ehd1.
authors.affiliation: Department of Life Science, Pohang University of Science and Technology (POSTECH), Pohang 790-784, Korea.
authors.forename: Yang-Seok
authors.initials: YS
authors.lastname: Lee
authors.forename: Dong-Hoon
authors.initials: DH
authors.lastname: Jeong
authors.forename: Dong-Yeon
authors.initials: DY
authors.lastname: Lee
authors.forename: Jakyung
authors.initials: J
authors.lastname: Yi
authors.forename: Choong-Hwan
authors.initials: CH
authors.lastname: Ryu
authors.forename: Song L
authors.initials: SL
authors.lastname: Kim
authors.forename: Hee J
authors.initials: HJ
authors.lastname: Jeong
authors.forename: Sang C
authors.initials: SC
authors.lastname: Choi
authors.forename: Ping
authors.initials: P
authors.lastname: Jin
authors.forename: Jungil
authors.initials: J
authors.lastname: Yang
authors.forename: Lae-Hyeon
authors.initials: LH
authors.lastname: Cho
authors.forename: Heebak
authors.initials: H
authors.lastname: Choi
authors.forename: Gynheung
authors.initials: G
authors.lastname: An
mesh_terms: D004269:DNA, Bacterial / Q000235:genetics; D035264:Flowers / Q000254:growth & development*; D018506:Gene Expression Regulation, Plant; D016254:Mutagenesis, Insertional; D009154:Mutation; D012275:Oryza / Q000235:genetics* / Q000378:metabolism; D017440:Photoperiod; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D018749:RNA, Plant / Q000235:genetics; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D004269:DNA, Bacterial; D010940:Plant Proteins; D018749:RNA, Plant; D012097:Repressor Proteins; C036483:T-DNA