title: Expression of turtle riboflavin-binding protein represses mitochondrial electron transport gene expression and promotes flowering in Arabidopsis.
abstract: BACKGROUND
  Recently we showed that de novo expression of a turtle riboflavin-binding protein (RfBP) in transgenic Arabidopsis increased H2O2 concentrations inside leaf cells, enhanced the expression of floral regulatory gene FD and floral meristem identity gene AP1 at the shoot apex, and induced early flowering. Here we report that RfBP-induced H2O2 presumably results from electron leakage at the mitochondrial electron transport chain (METC) and this source of H2O2 contributes to the early flowering phenotype.
  
  
  RESULTS
  While enhanced expression of FD and AP1 at the shoot apex was correlated with early flowering, the foliar expression of 13 of 19 METC genes was repressed in RfBP-expressing (RfBP+) plants. Inside RfBP+ leaf cells, cytosolic H2O2 concentrations were increased possibly through electron leakage because similar responses were also induced by a known inducer of electron leakage from METC. Early flowering no longer occurred when the repression on METC genes was eliminated by RfBP gene silencing, which restored RfBP+ to wild type in levels of FD and AP1 expression, H2O2, and flavins. Flowering was delayed by the external riboflavin application, which brought gene expression and flavins back to the steady-state levels but only caused 55% reduction of H2O2 concentrations in RfBP+ plants. RfBP-repressed METC gene expression remedied the cytosolic H2O2 diminution by genetic disruption of transcription factor NFXLl and compensated for compromises in FD and AP1 expression and flowering time. By contrast, RfBP resembled a peroxisomal catalase mutation, which augments the cytosolic H2O2, to enhance FD and AP1 expression and induce early flowering.
  
  
  CONCLUSIONS
  RfBP-repressed METC gene expression potentially causes electron leakage as one of cellular sources for the generation of H2O2 with the promoting effect on flowering. The repressive effect on METC gene expression is not the only way by which RfBP induces H2O2 and currently unappreciated factors may also function under RfBP+ background.
authors.forename: Liang
authors.initials: L
authors.lastname: Li
authors.forename: Li
authors.initials: L
authors.lastname: Hu
authors.forename: Li-Ping
authors.initials: LP
authors.lastname: Han
authors.forename: Hongtao
authors.initials: H
authors.lastname: Ji
authors.forename: Yueyue
authors.initials: Y
authors.lastname: Zhu
authors.forename: Xiaobing
authors.initials: X
authors.lastname: Wang
authors.forename: Jun
authors.initials: J
authors.lastname: Ge
authors.forename: Manyu
authors.initials: M
authors.lastname: Xu
authors.forename: Dan
authors.initials: D
authors.lastname: Shen
authors.forename: Hansong
authors.initials: H
authors.lastname: Dong
mesh_terms: D000818:Animals; D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D004579:Electron Transport / Q000235:genetics*; D035264:Flowers / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D018506:Gene Expression Regulation, Plant; D006861:Hydrogen Peroxide / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism; D018519:Meristem / Q000235:genetics / Q000378:metabolism; D008928:Mitochondria / Q000235:genetics*; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D014426:Turtles / Q000235:genetics
chemical_list: D029681:Arabidopsis Proteins; D026901:Membrane Transport Proteins; C019079:riboflavin-binding protein; D006861:Hydrogen Peroxide