Durum wheat mitochondria (DWM) possess an ATP-inhibited K+ channel, the plant mitoKATP (PmitoKATP), which is activated under environmental stress to control mitochondrial ROS production. To do this, PmitoKATP 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 PmitoKATP was activated by KCl. Contrarily, in control DWM, although PmitoKATP 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 PmitoKATP 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 PmitoKATP 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.
|Autori:||Trono, D. Soccio, M.;Laus, M.N.;Pastore D.|
|Data di pubblicazione:||2011|
|Titolo:||Potassium channel-oxidative phosphorylation relationship in durum wheat mitochondria from control and hyperosmotic-stressed seedlings|
|Rivista:||PLANT, CELL AND ENVIRONMENT|
|Appare nelle tipologie:||1.1 Articolo in rivista|