title: The antagonistic effect of hydroxyl radical on the development of a hypersensitive response in tobacco.
abstract: Reactive oxygen species (ROS) are important signalling molecules in living cells. It is believed that ROS molecules are the main triggers of the hypersensitive response (HR) in plants. In the present study of the effect of riboflavin, which is excited to generate ROS in light, on the development of the HR induced by the elicitin protein ParA1 in tobacco (Nicotiana tabacum), we found that the extent of the ParA1-induced HR was diminished by hydroxyl radical (OH•), a type of ROS. As compared with the zones treated with ParA1 only, the HR symptom in the zones that were infiltrated with ParA1 plus riboflavin was significantly diminished when the treated plants were placed in the light. However, this did not occur when the plants were maintained in the dark. Trypan blue staining and the ion leakage measurements confirmed HR suppression in the light. Further experiments proved that HR suppression is attributed to the involvement of the photoexcited riboflavin, and that the suppression can be eliminated with the addition of hydrogen peroxide scavengers or OH• scavengers. Fenton reagent treatment and EPR measurements demonstrated that it is OH• rather than hydrogen peroxide that contributes to HR suppression. Accompanying the endogenous OH• formation, suppression of the ParA1-induced HR occurred in the tobacco leaves that had been treated with high-level abscisic acid, and that suppression was also removed by OH• scavengers. These results offer evidence that OH•, an understudied and little appreciated ROS, participates in and modulates biologically relevant signalling in plant cells.
authors.affiliation: Key Laboratory of Monitoring and Management of Crop Diseases and Pest Insects, Ministry of Agricuture of People's Republic of China, Department of Plant Pathology, College of Plant Protection, Nanjing Agricultural University, Nanjing, China.
authors.forename: Sheng
authors.initials: S
authors.lastname: Deng
authors.forename: Mina
authors.initials: M
authors.lastname: Yu
authors.forename: Ying
authors.initials: Y
authors.lastname: Wang
authors.forename: Qin
authors.initials: Q
authors.lastname: Jia
authors.forename: Ling
authors.initials: L
authors.lastname: Lin
authors.forename: Hansong
authors.initials: H
authors.lastname: Dong
mesh_terms: D020418:Algal Proteins / Q000378:metabolism; D004578:Electron Spin Resonance Spectroscopy; D016166:Free Radical Scavengers / Q000494:pharmacology; D017665:Hydroxyl Radical / Q000378:metabolism*; D011506:Proteins; D017382:Reactive Oxygen Species / Q000378:metabolism; D012256:Riboflavin / Q000494:pharmacology; D015398:Signal Transduction; D014026:Nicotiana / Q000378:metabolism*
chemical_list: D020418:Algal Proteins; D016166:Free Radical Scavengers; D011506:Proteins; D017382:Reactive Oxygen Species; C085101:elicitin, Phytophthora; D017665:Hydroxyl Radical; D012256:Riboflavin