Mitochondria/nuclear signaling of alternative oxidase gene expression occurs through distinct pathways involving organic acids and reactive oxygen species.
Cultured cells of tobacco (Nicotiana tabacum L. cv Petit Havana) were used to investigate signals regulating the expression of the "model" nuclear gene encoding the alternative oxidase (AOX) (AOX1), the terminal oxidase of the mitochondrial alternative respiratory pathway. Several conditions shown to induce AOX1 mRNA accumulation also result in an increase in cellular citrate concentrations, suggesting that citrate and/or other tricarboxylic acid (TCA) cycle intermediates may be important signal metabolites. In addition, mitochondrial reactive oxygen species (ROS) production has recently been shown to be a factor mediating mitochondria-to-nucleus signaling for the expression of AOX1. We found that the exogenously supplied TCA cycle organic acids citrate, malate and 2-oxoglutarate caused rapid and dramatic increases in the steady-state level of AOX1 mRNA at low, near physiological concentrations (0.1 mM). Furthermore, an increase in AOX1 induced by the addition of organic acids occurs independently of mitochondrial ROS formation. Our results demonstrate that two separate pathways for mitochondria-to-nucleus signaling of AOX1 may exist, one involving ROS and the other organic acids.
Department of Plant Sciences, University of Saskatchewan, Saskatoon, SK, Canada, S7N 5A8. gr.gray@usask.ca
G R
GR
Gray
D P
DP
Maxwell
A R
AR
Villarimo
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L
McIntosh
D002467:Cell Nucleus / Q000235:genetics / Q000378:metabolism*; D002478:Cells, Cultured; D002952:Citric Acid Cycle / Q000235:genetics; D004734:Energy Metabolism / Q000235:genetics; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects / Q000235:genetics*; D018506:Gene Expression Regulation, Plant / Q000187:drug effects / Q000235:genetics; D008928:Mitochondria / Q000235:genetics / Q000378:metabolism*; D024101:Mitochondrial Proteins; D018384:Oxidative Stress / Q000187:drug effects / Q000235:genetics; D010088:Oxidoreductases / Q000096:biosynthesis / Q000235:genetics*; D010940:Plant Proteins; D012333:RNA, Messenger / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D014026:Nicotiana / Q000235:genetics / Q000378:metabolism*; D014233:Tricarboxylic Acids / Q000378:metabolism / Q000494:pharmacology; D015854:Up-Regulation / Q000187:drug effects / Q000235:genetics; D000099188:Alternative Oxidase
D024101:Mitochondrial Proteins; D010088:Oxidoreductases; D010940:Plant Proteins; D012333:RNA, Messenger; D017382:Reactive Oxygen Species; D014233:Tricarboxylic Acids; D000099188:Alternative Oxidase