title: Nitric oxide is involved in chitosan-induced systemic resistance in pearl millet against downy mildew disease.
abstract: BACKGROUND
  The nature and durability of resistance offered by chitosan and the involvement of nitric oxide (NO) in chitosan-induced defence reactions in pearl millet against downy mildew disease were investigated.
  
  
  RESULTS
  It had previously been reported that chitosan seed priming protected pearl millet plants against downy mildew disease. Further elucidation of the mechanism of resistance showed that chitosan seed priming protects the plants systemically. A minimum 4 day time gap is required between the chitosan treatment and pathogen inoculation for maximum resistance development, and it was found to be durable. Chitosan seed priming elevated NO accumulation in pearl millet seedlings, beginning from 2 h post-inoculation, and it was found to be involved in the activation of early defence reactions such as hypersensitive reaction, callose deposition and PR-1 protein expression. Pretreatment with NO scavenger C-PTIO and nitric oxide synthase (NOS) inhibitor L-NAME before pathogen inoculation reduced the disease-protecting ability of chitosan, and defence reactions were also downregulated, which indicated a possible role for NO in chitosan-induced resistance.
  
  
  CONCLUSIONS
  Protection offered by chitosan against pearl millet downy mildew disease is systemic in nature and durable. Chitosan-induced resistance is activated via NO signalling, as defence reactions induced by chitosan were downregulated under NO deficient conditions.
authors.affiliation: Downy Mildew Research Laboratory, Department of Applied Botany and Biotechnology, University of Mysore, Manasagangotri, Mysore-570006, Karnataka, India.
authors.forename: Girigowda
authors.initials: G
authors.lastname: Manjunatha
authors.forename: Sathyanaraya
authors.initials: S
authors.lastname: Niranjan-Raj
authors.forename: Geetha N
authors.initials: GN
authors.lastname: Prashanth
authors.forename: Shantharaj
authors.initials: S
authors.lastname: Deepak
authors.forename: Kestur N
authors.initials: KN
authors.lastname: Amruthesh
authors.forename: Hunthrike S
authors.initials: HS
authors.lastname: Shetty
mesh_terms: D048271:Chitosan / Q000276:immunology*; D007113:Immunity, Innate; D009569:Nitric Oxide / Q000276:immunology*; D009868:Oomycetes / Q000276:immunology / Q000502:physiology*; D031782:Pennisetum / Q000276:immunology* / Q000469:parasitology; D010935:Plant Diseases / Q000276:immunology* / Q000469:parasitology
chemical_list: D009569:Nitric Oxide; D048271:Chitosan