Article

Is the maintenance of homeostatic mitochondrial signaling during stress a physiological role for alternative oxidase?

Department of Biological Sciences, University of Toronto Scarborough, 1265 Military Trail, Toronto, Ontario M1C1A4, Canada.
Physiologia Plantarum (impact factor: 3.11). 06/2009; 137(4):392-406. DOI:10.1111/j.1399-3054.2009.01254.x pp.392-406
Source: PubMed

ABSTRACT All plants maintain a non-energy-conserving pathway of mitochondrial electron transport referred to as alternative oxidase (AOX) respiration. Here, we briefly review some of the most prevailing themes for the metabolic and physiological roles of this respiratory pathway. Many of these themes relate to the potential of AOX to provide metabolic homeostasis in response to fluctuating cellular conditions, such as is often seen during stress. We then review reverse genetic experiments that have been used to test these hypotheses. To date, such experiments have been limited to just two dicot species and have only targeted one member (a stress-induced member) of the AOX multigene family. Nonetheless, the experiments to date strongly reinforce the idea that AOX respiration is of particular importance during abiotic and biotic stress. Finally, we propose that another core role of AOX may be to modulate the strength of a stress-signaling pathway from the mitochondrion that controls cellular responses to stress. In this way, AOX could be acting to provide a degree of signaling homeostasis from the mitochondrion. This hypothesis may provide explanation for some of the disparate results seen in reverse genetic experiments regarding the impact of AOX on the reactive oxygen network and oxidative damage.

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Keywords

alternative oxidase
 
AOX
 
AOX multigene family
 
AOX respiration
 
biotic stress
 
controls cellular responses
 
metabolic homeostasis
 
mitochondrial electron transport
 
mitochondrion
 
modulate
 
non-energy-conserving pathway
 
physiological roles
 
prevailing themes
 
reactive oxygen network
 
respiratory pathway
 
reverse genetic experiments
 
signaling homeostasis
 
stress-induced member
 
stress-signaling pathway
 
two dicot species