title: A lack of mitochondrial alternative oxidase compromises capacity to recover from severe drought stress.
abstract: Alternative oxidase (AOX) constitutes a nonenergy conserving branch of the mitochondrial electron transport chain. AOX activity may be important to avoid reactive oxygen species (ROS) generation by the chain, particularly during abiotic stress. We compared leaf AOX1a transcript and AOX protein amounts in wild-type (WT) Nicotiana tabacum plants experiencing mild to severe drought. Mild to moderate drought resulted in a progressive and modest increase in AOX amount, accompanied by a progressive increased expression of different ROS-scavenging components. Under these conditions, transgenic plants with suppressed AOX amount, due to an RNA interference construct, were not compromised in their ability to manage ROS load and prevent cellular damage. Severe drought stress, particularly when combined with increased irradiance, strongly increased AOX amount in WT tobacco and this coincided with an increase in total respiration and, despite further induction of ROS-scavenging systems, some evidence of cellular damage. Under these severe conditions, plants lacking AOX suffered more cellular damage than WT and, at the most severe stage, were found to downregulate rather than upregulate the transcript level of several important ROS-scavenging components. At this stage, WT plants could still recover rapidly after rewatering, but the recoverability of AOX knockdown plants was strongly compromised.
authors.affiliation: Department of Biological Sciences and Department of Cell and Systems Biology, University of Toronto Scarborough, 1265 Military Trail, Toronto, ON, Canada, M1C 1A4.
authors.forename: Jia
authors.initials: J
authors.lastname: Wang
authors.affiliation: Department of Biological Sciences and Department of Cell and Systems Biology, University of Toronto Scarborough, 1265 Military Trail, Toronto, ON, Canada, M1C 1A4.
authors.forename: Greg C
authors.initials: GC
authors.lastname: Vanlerberghe
mesh_terms: D055864:Droughts; D018506:Gene Expression Regulation, Plant; D055785:Gene Knockdown Techniques; D008928:Mitochondria / Q000201:enzymology; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism*; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000378:metabolism*; D018515:Plant Leaves / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D018526:Plant Transpiration; D030821:Plants, Genetically Modified; D017382:Reactive Oxygen Species / Q000378:metabolism; D013312:Stress, Physiological; D014026:Nicotiana / Q000201:enzymology* / Q000235:genetics / Q000502:physiology; D000099188:Alternative Oxidase
chemical_list: D024101:Mitochondrial Proteins; D010088:Oxidoreductases; D010940:Plant Proteins; D017382:Reactive Oxygen Species; D000099188:Alternative Oxidase