title: Knockdown of mitochondrial alternative oxidase induces the 'stress state' of signaling molecule pools in Nicotiana tabacum, with implications for stomatal function.
abstract: The mitochondrial electron transport chain (ETC) includes an alternative oxidase (AOX) that may control the generation of reactive oxygen species (ROS) and reactive nitrogen species (RNS). ROS and RNS act as signaling intermediates in numerous plant processes, including stomatal movement. The role of AOX in controlling ROS and RNS concentrations under both steady-state and different stress conditions was evaluated using Nicotiana tabacum plants lacking AOX as a result of RNA interference. A potential functional implication of changes in ROS and RNS homeostasis was also evaluated by examining stomatal function. The leaves of nonstressed AOX knockdowns maintained concentrations of H2O2 and nitric oxide (NO) normally seen in wildtype plants only under stress conditions. Further, guard cell NO amounts were much higher in knockdowns. These guard cells were altered in size and were less responsive to NO as a signal for stomatal closure. This, in turn, compromised the stomatal response to changing irradiance. The results reveal a role for AOX in stomata. A working model is that guard cell AOX respiration maintains NO homeostasis by preventing over-reduction of the ETC, particularly during periods when high concentrations of NO acting as a signal for stomatal closure may also be inhibiting cyt oxidase respiration.
authors.affiliation: Department of Biological Sciences and Department of Cell and Systems Biology, University of Toronto Scarborough, 1265 Military Trail, Toronto, ON, M1C 1A4, Canada.
authors.forename: Marina
authors.initials: M
authors.lastname: Cvetkovska
authors.affiliation: Department of Biological Sciences and Department of Cell and Systems Biology, University of Toronto Scarborough, 1265 Military Trail, Toronto, ON, M1C 1A4, Canada.
authors.forename: Keshav
authors.initials: K
authors.lastname: Dahal
authors.affiliation: Department of Biological Sciences and Department of Cell and Systems Biology, University of Toronto Scarborough, 1265 Military Trail, Toronto, ON, M1C 1A4, Canada.
authors.forename: Nicole A
authors.initials: NA
authors.lastname: Alber
authors.affiliation: Department of Biological Sciences and Department of Cell and Systems Biology, University of Toronto Scarborough, 1265 Military Trail, Toronto, ON, M1C 1A4, Canada.
authors.forename: Cathy
authors.initials: C
authors.lastname: Jin
authors.affiliation: Department of Biological Sciences and Department of Cell and Systems Biology, University of Toronto Scarborough, 1265 Military Trail, Toronto, ON, M1C 1A4, Canada.
authors.forename: Melissa
authors.initials: M
authors.lastname: Cheung
authors.affiliation: Department of Biological Sciences and Department of Cell and Systems Biology, University of Toronto Scarborough, 1265 Military Trail, Toronto, ON, M1C 1A4, Canada.
authors.forename: Greg C
authors.initials: GC
authors.lastname: Vanlerberghe
mesh_terms: D055864:Droughts; D055785:Gene Knockdown Techniques; D006861:Hydrogen Peroxide / Q000378:metabolism; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism; D010088:Oxidoreductases / Q000235:genetics / Q000378:metabolism*; D059828:Plant Cells / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D054046:Plant Stomata / Q000235:genetics / Q000502:physiology*; D030821:Plants, Genetically Modified; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D013312:Stress, Physiological; D014026:Nicotiana / Q000235:genetics / Q000502:physiology*; D000099188:Alternative Oxidase
chemical_list: D006861:Hydrogen Peroxide; D024101:Mitochondrial Proteins; D009569:Nitric Oxide; D010088:Oxidoreductases; D010940:Plant Proteins; D017382:Reactive Oxygen Species; D000099188:Alternative Oxidase
keywords: Nicotiana tabacum (tobacco); alternative oxidase (AOX); drought; irradiance; mitochondria; nitric oxide (NO); signaling molecules; stomata