Aluminium triggers malate-independent potassium release via ion channels from the root apex in wheat.
The regulatory mechanisms for the aluminium (Al)-induced efflux of K(+) and malate from the root apex of Al-resistant wheat ( Triticum aestivum L. cv. Atlas) were characterized. Treatment with 20 mM tetraethylammonium (TEA) chloride, a K(+)-channel inhibitor, blocked the Al-induced K(+) efflux by 65%, but blocked the Al-induced malate efflux only slightly. Lanthanum (La(3+)) or ytterbium (Yb(3+)) strongly inhibited the K(+) efflux, but slightly increased malate efflux. These lanthanides applied together with Al did not affect the Al-induced malate efflux, but reduced the Al-induced K(+) efflux by 57% for La(3+) and by 35% for Yb(3+). By contrast, pretreatment with 50 microM niflumic acid, an anion-channel inhibitor, strongly suppressed the Al-induced malate efflux, but did not affect the Al-induced K(+) efflux. The efflux of K(+) uncoupled with that of malate resulted in the alkalization of intracellular pH in the root apex, suggesting that the release of K(+) coupled with malate plays an important role in stabilizing intracellular pH. Copper (Cu(2+)) induced the release of K(+) via a TEA-insensitive pathway without the release of malate in both Al-resistant and Al-sensitive (cultivar Scout) wheat. Simultaneous application of Al and Cu(2+) to the root apices resulted in TEA-sensitive K(+) efflux in Atlas but not in Scout, suggesting that Al competes with Cu(2+) for K(+) efflux. Taken together, these results suggest that Al-induced K(+) efflux is mediated by both TEA- and lanthanide-sensitive K(+) channels, although this induction is not a prerequisite for the induction of the release of malate.
Research Institute for Bioresources, Okayama University, Kurashiki, Japan.
Hiroki
H
Osawa
Hideaki
H
Matsumoto
D000535:Aluminum / Q000494:pharmacology*; D002478:Cells, Cultured; D003300:Copper / Q000494:pharmacology; D007811:Lanthanum / Q000494:pharmacology; D008293:Malates / Q000378:metabolism*; D018517:Plant Roots / Q000187:drug effects / Q000502:physiology*; D011188:Potassium / Q000378:metabolism*; D015221:Potassium Channels / Q000502:physiology*; D019789:Tetraethylammonium / Q000494:pharmacology; D014908:Triticum / Q000187:drug effects / Q000502:physiology*; D015018:Ytterbium / Q000494:pharmacology
D008293:Malates; D015221:Potassium Channels; D019789:Tetraethylammonium; D007811:Lanthanum; D003300:Copper; C030298:malic acid; D000535:Aluminum; D015018:Ytterbium; D011188:Potassium