Alternative oxidase modulates leaf mitochondrial concentrations of superoxide and nitric oxide

Authors

  • Marina Cvetkovska,

    1. Department of Biological Sciences and Department of Cell and Systems Biology, University of Toronto Scarborough, 1265 Military Trail, Toronto, ON, Canada M1C 1A4
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  • Greg C. Vanlerberghe

    1. Department of Biological Sciences and Department of Cell and Systems Biology, University of Toronto Scarborough, 1265 Military Trail, Toronto, ON, Canada M1C 1A4
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Author for correspondence:
Greg C. Vanlerberghe
Tel: +1 416 287 7431
Email: gregv@utsc.utoronto.ca

Summary

  • The nonenergy-conserving alternative oxidase (AOX) has been hypothesized to modulate the amount of reactive oxygen species (ROS) and reactive nitrogen species (RNS) in plant mitochondria but there is sparse direct in planta evidence to support this.
  • Laser scanning fluorescent confocal microscopy and biochemical methods were used to directly estimate in planta leaf concentrations of superoxide (inline image), nitric oxide (NO), peroxynitrite (ONOO) and hydrogen peroxide (H2O2) in wildtype (Wt) tobacco (Nicotiana tabacum) and transgenic tobacco with altered amounts of AOX.
  • We found that plants lacking AOX have increased concentrations of leaf mitochondrial-localized inline image and leaf NO in comparison to the Wt, while leaf concentrations of H2O2 were similar or lower in the AOX-suppressed plants.
  • Based on our results, we suggest that AOX respiration acts to reduce the generation of ROS and RNS in plant mitochondria by dampening the leak of single electrons from the electron transport chain to O2 or nitrite. This may represent a universal role for AOX in plants. More work is now needed to establish the functional implications of this role, such as during abiotic and biotic stress.

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