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Polyamines Interact with Hydroxyl Radicals in Activating Ca²⁺ and K⁺ Transport across the Root Epidermal Plasma Membranes

Isaac Zepeda-Jazo, Ana María Velarde-Buendía, René Enríquez-Figueroa, Jayakumar Bose, Sergey Shabala, Jesús Muñiz-Murguía and Igor I. Pottosin
Plant Physiology
Vol. 157, No. 4 (December 2011), pp. 2167-2180
Stable URL: http://www.jstor.org/stable/41435659
Page Count: 14
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Polyamines Interact with Hydroxyl Radicals in Activating Ca²⁺ and K⁺ Transport across the Root Epidermal Plasma Membranes
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Abstract

Reactive oxygen species (ROS) are integral components of the plant adaptive responses to environment. Importantly, ROS affect the intracellular Ca²⁺ dynamics by activating a range of nonselective Ca²⁺-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 Ca²⁺ fluxes induced by hydroxyl radicals (OH*) in pea (Pisum sativum) roots. OH*, but not hydrogen peroxide, activated a rapid Ca²⁺ efflux and a more slowly developing net Ca²⁺ 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 Ca²⁺. Active OH*-induced Ca²⁺ efflux in roots was suppressed by the PM Ca²⁺ 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 Ca²⁺ influx in roots. Contrary to expectations, polyamines (PAs) did not inhibit the OH*-induced cation fluxes. The net OH*-induced Ca²⁺ 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 Ca²⁺ homeostasis by modulating both Ca²⁺ influx and efflux transport systems at the root cell PM.

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