title: Expression of FcFT1, a FLOWERING LOCUS T-like gene, is regulated by light and associated with inflorescence differentiation in fig (Ficus carica L.).
abstract: BACKGROUND
  Because the floral induction occurs in many plants when specific environmental conditions are satisfied, most plants bloom and bear fruit during the same season each year. In fig, by contrast, the time interval during which inflorescence (flower bud, fruit) differentiation occurs corresponds to the shoot elongation period. Fig trees thus differ from many species in their reproductive growth characteristics. To date, however, the molecular mechanisms underlying this unorthodox physiology of floral induction and fruit setting in fig trees have not been elucidated.
  
  
  RESULTS
  We isolated a FLOWERING LOCUS T (FT)-like gene from fig and examined its function, characteristics, and expression patterns. The isolated gene, F. carica FT (FcFT1), is single copy in fig and shows the highest similarity at the amino acid level (93.1%) to apple MdFT2. We sequenced its upstream region (1,644 bp) and identified many light-responsive elements. FcFT1 was mainly expressed in leaves and induced early flowering in transgenic tobacco, suggesting that FcFT1 is a fig FT ortholog. Real-time reverse-transcription PCR analysis revealed that FcFT1 mRNA expression occurred only in leaves at the lower nodes, the early fruit setting positions. mRNA levels remained a constant for approximately 5 months from spring to autumn, corresponding almost exactly to the inflorescence differentiation season. Diurnal variation analysis revealed that FcFT1 mRNA expression increased under relative long-day and short-day conditions, but not under continuous darkness.
  
  
  CONCLUSIONS
  These results suggest that FcFT1 activation is regulated by light conditions and may contribute to fig's unique fruit-setting characteristics.
authors.affiliation: Fukuoka Agricultural Research Center, 587 Yoshiki, Chikushino, Fukuoka 818-8549, Japan. ikegami@farc.pref.fukuoka.jp.
authors.forename: Hidetoshi
authors.initials: H
authors.lastname: Ikegami
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Nogata
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Inoue
authors.forename: Shuichi
authors.initials: S
authors.lastname: Himeno
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Yakushiji
authors.forename: Chiharu
authors.initials: C
authors.lastname: Hirata
authors.forename: Keita
authors.initials: K
authors.lastname: Hirashima
authors.forename: Masashi
authors.initials: M
authors.lastname: Mori
authors.forename: Mitsuo
authors.initials: M
authors.lastname: Awamura
authors.forename: Takao
authors.initials: T
authors.lastname: Nakahara
mesh_terms: D002940:Circadian Rhythm / Q000235:genetics; D030681:Ficus / Q000235:genetics* / Q000254:growth & development* / Q000528:radiation effects; D005638:Fruit / Q000235:genetics; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant / Q000528:radiation effects*; D017343:Genes, Plant / Q000235:genetics*; D056626:Inflorescence / Q000235:genetics / Q000254:growth & development* / Q000528:radiation effects; D008027:Light; D010641:Phenotype; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D030821:Plants, Genetically Modified; D011401:Promoter Regions, Genetic / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D014026:Nicotiana / Q000235:genetics
chemical_list: D010940:Plant Proteins; D012333:RNA, Messenger