title: Polyamines interact with hydroxyl radicals in activating Ca(2+) and K(+) transport across the root epidermal plasma membranes.
abstract: Reactive oxygen species (ROS) are integral components of the plant adaptive responses to environment. Importantly, ROS affect the intracellular Ca(2+) dynamics by activating a range of nonselective Ca(2+)-permeable channels in plasma membrane (PM). Using patch-clamp and noninvasive microelectrode ion flux measuring techniques, we have characterized ionic currents and net K(+) and Ca(2+) fluxes induced by hydroxyl radicals (OH(•)) in pea (Pisum sativum) roots. OH(•), but not hydrogen peroxide, activated a rapid Ca(2+) efflux and a more slowly developing net Ca(2+) influx concurrent with a net K(+) efflux. In isolated protoplasts, OH(•) evoked a nonselective current, with a time course and a steady-state magnitude similar to those for a K(+) efflux in intact roots. This current displayed a low ionic selectivity and was permeable to Ca(2+). Active OH(•)-induced Ca(2+) efflux in roots was suppressed by the PM Ca(2+) pump inhibitors eosine yellow and erythrosine B. The cation channel blockers gadolinium, nifedipine, and verapamil and the anionic channel blockers 5-nitro-2(3-phenylpropylamino)-benzoate and niflumate inhibited OH(•)-induced ionic currents in root protoplasts and K(+) efflux and Ca(2+) influx in roots. Contrary to expectations, polyamines (PAs) did not inhibit the OH(•)-induced cation fluxes. The net OH(•)-induced Ca(2+) efflux was largely prolonged in the presence of spermine, and all PAs tested (spermine, spermidine, and putrescine) accelerated and augmented the OH(•)-induced net K(+) efflux from roots. The latter effect was also observed in patch-clamp experiments on root protoplasts. We conclude that PAs interact with ROS to alter intracellular Ca(2+) homeostasis by modulating both Ca(2+) influx and efflux transport systems at the root cell PM.
authors: Centro Universitario de Investigaciones Biomédicas, Universidad de Colima, 28045 Colima, Mexico.
authors: Isaac
authors: I
authors: Zepeda-Jazo
authors: Ana María
authors: AM
authors: Velarde-Buendía
authors: René
authors: R
authors: Enríquez-Figueroa
authors: Jayakumar
authors: J
authors: Bose
authors: Sergey
authors: S
authors: Shabala
authors: Jesús
authors: J
authors: Muñiz-Murguía
authors: Igor I
authors: II
authors: Pottosin
mesh_terms: D002118:Calcium / Q000032:analysis / Q000493:pharmacokinetics*; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D006706:Homeostasis; D017665:Hydroxyl Radical / Q000032:analysis / Q000494:pharmacology*; D017136:Ion Transport; D008564:Membrane Potentials / Q000187:drug effects; D018408:Patch-Clamp Techniques; D018532:Pisum sativum / Q000187:drug effects / Q000502:physiology*; D019441:Plant Epidermis / Q000187:drug effects / Q000502:physiology; D018517:Plant Roots / Q000187:drug effects / Q000502:physiology; D011073:Polyamines / Q000378:metabolism*; D011188:Potassium / Q000032:analysis / Q000493:pharmacokinetics*; D011523:Protoplasts; D017382:Reactive Oxygen Species / Q000032:analysis / Q000494:pharmacology; D013045:Species Specificity
chemical_list: D011073:Polyamines; D017382:Reactive Oxygen Species; D017665:Hydroxyl Radical; D011188:Potassium; D002118:Calcium