Coordination of a mitochondrial superoxide burst during the hypersensitive response to bacterial pathogen in Nicotiana tabacum.
We characterized responses of Nicotiana tabacum to pathovars of the bacterial pathogen Pseudomonas syringae. These included a compatible response associated with necrotic cell death (pv. tabaci), an incompatible response that included hypersensitive response (HR) cell death (pv. maculicola) and an incompatible response that induced defences but lacked the HR (pv. phaseolicola). Signalling molecules (salicylic acid, nitric oxide, H(2)O(2)) known to induce the stress responsive tobacco Aox1a gene [that encodes the mitochondrial electron transport chain (ETC) component alternative oxidase (AOX)] accumulated preferentially during the HR, but this did not elevate Aox1a transcript or AOX protein, while the transcript and protein were strongly elevated during the defence response to pv. phaseolicola. In addition, matrix manganese superoxide dismutase (MnSOD) activity declined during the HR, unlike its response to the other pathovars, and unlike the response of other superoxide dismutase (SOD) enzymes. Finally, the HR (but not the response to pv. phaseolicola or pv. tabaci) was accompanied by an early and persistent mitochondrial superoxide (O(2)(-)) burst prior to cell death. We propose that a coordinated response of the major ETC mechanism to avoid O(2)(-) generation (AOX) and the sole enzymatic means to scavenge mitochondrial O(2)(-) (MnSOD) is important in the determination of cell fate during responses to pathogen.
Department of Biological Sciences, University of Toronto Scarborough, Toronto, Ontario, Canada M1C 1A4.
Marina
M
Cvetkovska
Greg C
GC
Vanlerberghe
D016923:Cell Death; D018506:Gene Expression Regulation, Plant; D054884:Host-Pathogen Interactions; D006861:Hydrogen Peroxide / Q000032:analysis; D008928:Mitochondria / Q000378:metabolism*; D024101:Mitochondrial Proteins / Q000378:metabolism; D009569:Nitric Oxide / Q000032:analysis; D010088:Oxidoreductases / Q000378:metabolism; D010935:Plant Diseases / Q000382:microbiology; D018515:Plant Leaves / Q000382:microbiology / Q000502:physiology; D010940:Plant Proteins / Q000378:metabolism; D044224:Pseudomonas syringae / Q000472:pathogenicity*; D020156:Salicylic Acid / Q000032:analysis; D013482:Superoxide Dismutase / Q000378:metabolism; D013481:Superoxides / Q000378:metabolism*; D014026:Nicotiana / Q000235:genetics / Q000382:microbiology / Q000502:physiology*; D000099188:Alternative Oxidase
D006861:Hydrogen Peroxide; D024101:Mitochondrial Proteins; D009569:Nitric Oxide; D010088:Oxidoreductases; D010940:Plant Proteins; D020156:Salicylic Acid; D013482:Superoxide Dismutase; D013481:Superoxides; D000099188:Alternative Oxidase