Changes in plant mitochondrial electron transport alter cellular levels of reactive oxygen species and susceptibility to cell death signaling molecules.
Transgenic tobacco (Nicotiana tabacum) lacking mitochondrial alternative oxidase (AOX) have been compared with wild-type (Wt) tobacco using two different systems, either suspension cell cultures or leaves. In both systems, a lack of AOX was accompanied by an increase in some anti-oxidant defenses, consistent with the hypothesis that a lack of AOX increases the mitochondrial generation of reactive oxygen species (ROS). In most cases, this increase in anti-oxidant defenses could more than offset the presumed increased rate of ROS generation, resulting paradoxically in a lower steady-state level of ROS than was found in Wt leaves or suspension cells. We also found that the amount of cell death induced by salicylic acid or nitric oxide correlated strongly with the level of ROS (irrespective of the level of AOX), while death induced by azide was dependent upon the presence or absence of AOX. These results suggest that susceptibility to cell death by signaling molecules (salicylic acid and nitric oxide) is dependent upon the steady-state cellular level of ROS and that AOX levels clearly contribute to this steady state, perhaps by influencing the rate of mitochondrial-generated ROS and hence the cellular level of anti-oxidant defenses.
Amirsadeghi
Sasan
S
Department of Life Sciences, University of Toronto Scarborough, 1265 Military Trail, Toronto, ON, Canada M1C1A4.
Robson
Christine A
CA
McDonald
Allison E
AE
Vanlerberghe
Greg C
GC
D000975:Antioxidants / Q000378:metabolism; D016923:Cell Death / Q000187:drug effects; D004579:Electron Transport / Q000187:drug effects*; D003576:Electron Transport Complex IV / Q000378:metabolism; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D017343:Genes, Plant; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism*; D024101:Mitochondrial Proteins; D009569:Nitric Oxide / Q000494:pharmacology*; D010088:Oxidoreductases / Q000172:deficiency; D018515:Plant Leaves / Q000187:drug effects; D010940:Plant Proteins / Q000378:metabolism; D030821:Plants, Genetically Modified; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism*; D020156:Salicylic Acid / Q000494:pharmacology*; D014026:Nicotiana / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D015854:Up-Regulation / Q000187:drug effects; D000099188:Alternative Oxidase
D000975:Antioxidants; D003576:Electron Transport Complex IV; D024101:Mitochondrial Proteins; D009569:Nitric Oxide; D010088:Oxidoreductases; D010940:Plant Proteins; D012333:RNA, Messenger; D017382:Reactive Oxygen Species; D020156:Salicylic Acid; D000099188:Alternative Oxidase