title: Down-regulation of free riboflavin content induces hydrogen peroxide and a pathogen defense in Arabidopsis.
abstract: Riboflavin mediates many bioprocesses associated with the generation of hydrogen peroxide (H₂O₂), a cellular signal that regulates defense responses in plants. Although plants can synthesize riboflavin, the levels vary widely in different organs and during different stages of development, indicating that changes in riboflavin levels may have physiological effects. Here, we show that changing riboflavin content affects H₂O₂ accumulation and a pathogen defense in Arabidopsis thaliana. Leaf content of free riboflavin was modulated by ectopic expression of the turtle gene encoding riboflavin-binding protein (RfBP). The RfBP-expressing Arabidopsis thaliana (REAT) plants produced the RfBP protein that possessed riboflavin-binding activity. Compared with the wild-type plant, several tested REAT lines had >70% less flavins of free form. This change accompanied an elevation in the level of H₂O₂ and an enhancement of plant resistance to a bacterial pathogen. All the observed REAT characters were eliminated due to RfBP silencing (RfBPi) under REAT background. When an H₂O₂ scavenger was applied, H₂O₂ level declined in all the plants, and REAT no longer exhibited the phenotype of resistance enhancement. However, treatment with an NADPH oxidase inhibitor diminished H₂O₂ content and pathogen defense in wild-type and RfBPi but not in REAT. Our results suggest that the intrinsic down-regulation of free flavins is responsible for NADPH oxidase-independent H₂O₂ accumulation and the pathogen defense.
authors: State Ministry of Education Key Laboratory of Integrated Management of Crop Pests, Nanjing Agricultural University, Nanjing 210095, China.
authors: Benliang
authors: B
authors: Deng
authors: Sheng
authors: S
authors: Deng
authors: Feng
authors: F
authors: Sun
authors: Shujian
authors: S
authors: Zhang
authors: Hansong
authors: H
authors: Dong
mesh_terms: D000818:Animals; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism* / Q000382:microbiology; D029681:Arabidopsis Proteins / Q000378:metabolism; D015536:Down-Regulation; D006861:Hydrogen Peroxide / Q000378:metabolism*; D007113:Immunity, Innate; D019255:NADPH Oxidases / Q000378:metabolism; D010641:Phenotype; D030821:Plants, Genetically Modified / Q000378:metabolism / Q000382:microbiology; D012256:Riboflavin / Q000235:genetics / Q000378:metabolism*; D014426:Turtles / Q000235:genetics
chemical_list: D029681:Arabidopsis Proteins; D006861:Hydrogen Peroxide; D019255:NADPH Oxidases; D012256:Riboflavin