title: Orchestration of hydrogen peroxide and nitric oxide in brassinosteroid-mediated systemic virus resistance in Nicotiana benthamiana.
abstract: Brassinosteroids (BRs) play essential roles in modulating plant growth, development and stress responses. Here, involvement of BRs in plant systemic resistance to virus was studied. Treatment of local leaves in Nicotiana benthamiana with BRs induced virus resistance in upper untreated leaves, accompanied by accumulations of H2O2 and NO. Scavenging of H2O2 or NO in upper leaves blocked BR-induced systemic virus resistance. BR-induced systemic H2O2 accumulation was blocked by local pharmacological inhibition of NADPH oxidase or silencing of respiratory burst oxidase homolog gene NbRBOHB, but not by systemic NADPH oxidase inhibition or NbRBOHA silencing. Silencing of the nitrite-dependent nitrate reductase gene NbNR or systemic pharmacological inhibition of NR compromised BR-triggered systemic NO accumulation, while local inhibition of NR, silencing of NbNOA1 and inhibition of NOS had little effect. Moreover, we provide evidence that BR-activated H2O2 is required for NO synthesis. Pharmacological scavenging or genetic inhibiting of H2O2 generation blocked BR-induced systemic NO production, but BR-induced H2O2 production was not sensitive to NO scavengers or silencing of NbNR. Systemically applied sodium nitroprusside rescued BR-induced systemic virus defense in NbRBOHB-silenced plants, but H2O2 did not reverse the effect of NbNR silencing on BR-induced systemic virus resistance. Finally, we demonstrate that the receptor kinase BRI1(BR insensitive 1) is an upstream component in BR-mediated systemic defense signaling, as silencing of NbBRI1 compromised the BR-induced H2O2 and NO production associated with systemic virus resistance. Together, our pharmacological and genetic data suggest the existence of a signaling pathway leading to BR-mediated systemic virus resistance that involves local Respiratory Burst Oxidase Homolog B (RBOHB)-dependent H2O2 production and subsequent systemic NR-dependent NO generation.
authors.affiliation: Ministry of Education Key Laboratory for Bio-Resource and Eco-Environment, College of Life Science, State Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan University, Chengdu, 610064, China.
authors.forename: Xing-Guang
authors.initials: XG
authors.lastname: Deng
authors.affiliation: Ministry of Education Key Laboratory for Bio-Resource and Eco-Environment, College of Life Science, State Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan University, Chengdu, 610064, China.
authors.forename: Tong
authors.initials: T
authors.lastname: Zhu
authors.affiliation: Ministry of Education Key Laboratory for Bio-Resource and Eco-Environment, College of Life Science, State Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan University, Chengdu, 610064, China.
authors.forename: Li-Juan
authors.initials: LJ
authors.lastname: Zou
authors.affiliation: Ministry of Education Key Laboratory for Bio-Resource and Eco-Environment, College of Life Science, State Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan University, Chengdu, 610064, China.
authors.forename: Xue-Ying
authors.initials: XY
authors.lastname: Han
authors.affiliation: Ministry of Education Key Laboratory for Bio-Resource and Eco-Environment, College of Life Science, State Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan University, Chengdu, 610064, China.
authors.forename: Xue
authors.initials: X
authors.lastname: Zhou
authors.affiliation: Ministry of Education Key Laboratory for Bio-Resource and Eco-Environment, College of Life Science, State Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan University, Chengdu, 610064, China.
authors.forename: De-Hui
authors.initials: DH
authors.lastname: Xi
authors.affiliation: Ministry of Education Key Laboratory for Bio-Resource and Eco-Environment, College of Life Science, State Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan University, Chengdu, 610064, China.
authors.forename: Da-Wei
authors.initials: DW
authors.lastname: Zhang
authors.affiliation: Ministry of Education Key Laboratory for Bio-Resource and Eco-Environment, College of Life Science, State Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan University, Chengdu, 610064, China.
authors.forename: Hong-Hui
authors.initials: HH
authors.lastname: Lin
mesh_terms: D060406:Brassinosteroids / Q000378:metabolism*; D060467:Disease Resistance; D018506:Gene Expression Regulation, Plant; D017930:Genes, Reporter; D006861:Hydrogen Peroxide / Q000378:metabolism*; D008954:Models, Biological; D019255:NADPH Oxidases / Q000235:genetics / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism*; D010935:Plant Diseases / Q000276:immunology*; D018515:Plant Leaves / Q000166:cytology / Q000235:genetics / Q000276:immunology; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction; D014026:Nicotiana / Q000166:cytology / Q000235:genetics / Q000276:immunology*; D014027:Tobacco Mosaic Virus / Q000472:pathogenicity
chemical_list: D060406:Brassinosteroids; D010940:Plant Proteins; D017382:Reactive Oxygen Species; D009569:Nitric Oxide; D006861:Hydrogen Peroxide; D019255:NADPH Oxidases; C022709:superoxide-forming enzyme
keywords: Nicotiana benthamiana; brassinosteroids; hydrogen peroxide; nitric oxide; systemic virus resistance; virus-induced gene silencing