Arabidopsis root K+-efflux conductance activated by hydroxyl radicals: single-channel properties, genetic basis and involvement in stress-induced cell death.
Reactive oxygen species (ROS) are central to plant stress response, signalling, development and a multitude of other processes. In this study, the plasma-membrane hydroxyl radical (HR)-activated K(+) channel responsible for K(+) efflux from root cells during stress accompanied by ROS generation is characterised. The channel showed 16-pS unitary conductance and was sensitive to Ca(2+), tetraethylammonium, Ba(2+), Cs(+) and free-radical scavengers. The channel was not found in the gork1-1 mutant, which lacks a major plasma-membrane outwardly rectifying K(+) channel. In intact Arabidopsis roots, both HRs and stress induced a dramatic K(+) efflux that was much smaller in gork1-1 plants. Tests with electron paramagnetic resonance spectroscopy showed that NaCl can stimulate HR generation in roots and this might lead to K(+)-channel activation. In animals, activation of K(+)-efflux channels by HRs can trigger programmed cell death (PCD). PCD symptoms in Arabidopsis roots developed much more slowly in gork1-1 and wild-type plants treated with K(+)-channel blockers or HR scavengers. Therefore, similar to animal counterparts, plant HR-activated K(+) channels are also involved in PCD. Overall, this study provides new insight into the regulation of plant cation transport by ROS and demonstrates possible physiological properties of plant HR-activated K(+) channels.
Demidchik
Vadim
V
Department of Biological Sciences, University of Essex, Colchester, Essex CO4 5AP, UK. vdemid@essex.ac.uk
Cuin
Tracey A
TA
Svistunenko
Dimitri
D
Smith
Susan J
SJ
Miller
Anthony J
AJ
Shabala
Sergey
S
Sokolik
Anatoliy
A
Yurin
Vladimir
V
D017360:Arabidopsis / Q000166:cytology* / Q000187:drug effects / Q000235:genetics*; D029681:Arabidopsis Proteins / Q000378:metabolism; D001205:Ascorbic Acid / Q000494:pharmacology; D016923:Cell Death / Q000187:drug effects; D003300:Copper / Q000494:pharmacology; D004578:Electron Spin Resonance Spectroscopy; D006861:Hydrogen Peroxide / Q000494:pharmacology; D017665:Hydroxyl Radical / Q000494:pharmacology*; D020287:In Situ Nick-End Labeling; D015640:Ion Channel Gating / Q000187:drug effects*; D008564:Membrane Potentials / Q000187:drug effects; D008954:Models, Biological; D009154:Mutation / Q000235:genetics; D018408:Patch-Clamp Techniques; D019441:Plant Epidermis / Q000187:drug effects / Q000378:metabolism; D018517:Plant Roots / Q000166:cytology* / Q000187:drug effects / Q000235:genetics / Q000254:growth & development; D015221:Potassium Channels / Q000378:metabolism*; D011523:Protoplasts / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D012965:Sodium Chloride / Q000494:pharmacology; D013312:Stress, Physiological / Q000187:drug effects*
D029681:Arabidopsis Proteins; D015221:Potassium Channels; D017665:Hydroxyl Radical; D012965:Sodium Chloride; D003300:Copper; D006861:Hydrogen Peroxide; D001205:Ascorbic Acid