Polyamines interact with hydroxyl radicals in activating Ca(2+) and K(+) transport across the root epidermal plasma membranes

• Published in: Plant physiology (Bethesda) Vol. 157; no. 4; p. 2167
• Main Authors: Zepeda-Jazo, Isaac, Velarde-Buendía, Ana María, Enríquez-Figueroa, René, Bose, Jayakumar, Shabala, Sergey, Muñiz-Murguía, Jesús, Pottosin, Igor I
• Format: Journal Article
• Language: English
• Published: United States 01.12.2011
• Subjects: Calcium - analysis; Calcium - pharmacokinetics; Cell Membrane - drug effects; Cell Membrane - metabolism; Homeostasis; Hydroxyl Radical - analysis; Hydroxyl Radical - pharmacology; Ion Transport; Membrane Potentials - drug effects; Patch-Clamp Techniques; Pisum sativum - drug effects; Pisum sativum - physiology; Plant Epidermis - drug effects; Plant Epidermis - physiology; Plant Roots - drug effects; Plant Roots - physiology; Polyamines - metabolism; Potassium - analysis; Potassium - pharmacokinetics; Protoplasts; Reactive Oxygen Species - analysis; Reactive Oxygen Species - pharmacology; Species Specificity
• ISSN: 1532-2548
• DOI: 10.1104/pp.111.179671

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.