title: Potassium channel-oxidative phosphorylation relationship in durum wheat mitochondria from control and hyperosmotic-stressed seedlings.
abstract: Durum wheat mitochondria (DWM) possess an ATP-inhibited K(+)  channel, the plant mitoK(ATP)  (PmitoK(ATP) ), which is activated under environmental stress to control mitochondrial ROS production. To do this, PmitoK(ATP)  collapses membrane potential (ΔΨ), thus suggesting mitochondrial uncoupling. We tested this point by studying oxidative phosphorylation (OXPHOS) in DWM purified from control seedlings and from seedlings subjected both to severe mannitol and NaCl stress. In severely-stressed DWM, the ATP synthesis via OXPHOS, continuously monitored by a spectrophotometric assay, was about 90% inhibited when the PmitoK(ATP)  was activated by KCl. Contrarily, in control DWM, although PmitoK(ATP)  collapsed ΔΨ, ATP synthesis, as well as coupling [respiratory control (RC) ratio and ratio between phosphorylated ADP and reduced oxygen (ADP/O)] checked by oxygen uptake experiments, were unaffected. We suggest that PmitoK(ATP)  may play an important defensive role at the onset of the environmental/oxidative stress by preserving energy in a crucial moment for cell and mitochondrial bioenergetics. Consistently, under moderate mannitol stress, miming an early stress condition, the channel may efficiently control reactive oxygen species (ROS) generation (about 35-fold from fully open to closed state) without impairing ATP synthesis. Anyway, if the stress significantly proceeds, the PmitoK(ATP)  becomes fully activated by decrease of ATP concentration (25-40%) and increase of activators [free fatty acids (FFAs) and superoxide anion], thus impairing ATP synthesis.
authors.affiliation: CRA - Centro di Ricerca per la Cerealicoltura, S.S. 16 Km 675, Dipartimento di Scienze Agroambientali, Chimica e Difesa Vegetale, Università di Foggia, Via Napoli 25, Italy.
authors.forename: Daniela
authors.initials: D
authors.lastname: Trono
authors.forename: Mario
authors.initials: M
authors.lastname: Soccio
authors.forename: Maura N
authors.initials: MN
authors.lastname: Laus
authors.forename: Donato
authors.initials: D
authors.lastname: Pastore
mesh_terms: D000255:Adenosine Triphosphate / Q000096:biosynthesis; D006863:Hydrogen-Ion Concentration; D008353:Mannitol; D053078:Membrane Potential, Mitochondrial; D008928:Mitochondria / Q000378:metabolism*; D009995:Osmosis; D010085:Oxidative Phosphorylation; D010100:Oxygen / Q000378:metabolism; D010940:Plant Proteins / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism; D015221:Potassium Channels / Q000378:metabolism*; D036226:Seedlings / Q000378:metabolism; D012965:Sodium Chloride; D013312:Stress, Physiological; D013481:Superoxides / Q000378:metabolism; D014908:Triticum / Q000378:metabolism*
chemical_list: D010940:Plant Proteins; D015221:Potassium Channels; C117780:mitochondrial K(ATP) channel; D013481:Superoxides; D008353:Mannitol; D012965:Sodium Chloride; D000255:Adenosine Triphosphate; D011188:Potassium; D010100:Oxygen