Free oxygen radicals regulate plasma membrane Ca2+- and K+-permeable channels in plant root cells.
Free oxygen radicals are an irrefutable component of life, underlying important biochemical and physiological phenomena in animals. Here it is shown that free oxygen radicals activate plasma membrane Ca(2+)- and K(+)-permeable conductances in Arabidopsis root cell protoplasts, mediating Ca(2+) influx and K(+) efflux, respectively. Free oxygen radicals generate increases in cytosolic Ca(2+) mediated by a novel population of nonselective cation channels that differ in selectivity and pharmacology from those involved in toxic Na(+) influx. Analysis of the free oxygen radical-activated K(+) conductance showed its similarity to the Arabidopsis root K(+) outward rectifier. Significantly larger channel activation was found in cells responsible for perceiving environmental signals and undergoing elongation. Quenching root free oxygen radicals inhibited root elongation, confirming the role of radical-activated Ca(2+) influx in cell growth. Net free oxygen radical-stimulated Ca(2+) influx and K(+) efflux were observed in root cells of monocots, dicots, C3 and C4 plants, suggesting conserved mechanisms and functions. In conclusion, two functions for free oxygen radical cation channel activation are proposed: initialization/amplification of stress signals and control of cell elongation in root growth.
Demidchik
Vadim
V
Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EA, UK. vd211@cam.ac.uk
Shabala
Sergey N
SN
Coutts
Katherine B
KB
Tester
Mark A
MA
Davies
Julia M
JM
D017360:Arabidopsis / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000187:drug effects / Q000378:metabolism*; D002455:Cell Division / Q000187:drug effects / Q000502:physiology; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D002463:Cell Membrane Permeability / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D003300:Copper / Q000494:pharmacology; D016166:Free Radical Scavengers / Q000494:pharmacology; D017665:Hydroxyl Radical / Q000378:metabolism / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D018384:Oxidative Stress / Q000187:drug effects / Q000502:physiology; D019441:Plant Epidermis / Q000187:drug effects / Q000378:metabolism; D018517:Plant Roots / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism; D015221:Potassium Channels / Q000187:drug effects / Q000378:metabolism*; D017382:Reactive Oxygen Species / Q000378:metabolism* / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology
D015220:Calcium Channels; D016166:Free Radical Scavengers; D015221:Potassium Channels; D017382:Reactive Oxygen Species; D017665:Hydroxyl Radical; D003300:Copper; D011188:Potassium; D002118:Calcium