Journal Article

Plant Inner Membrane Anion Channel (PIMAC) Function in Plant Mitochondria

Maura Nicoletta Laus, Mario Soccio, Daniela Trono, Luigi Cattivelli and Donato Pastore

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 49, issue 7, pages 1039-1055
Published in print July 2008 | ISSN: 0032-0781
Published online May 2008 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pcn082
Plant Inner Membrane Anion Channel (PIMAC) Function in Plant Mitochondria

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  • Biochemistry
  • Molecular and Cell Biology
  • Plant Sciences and Forestry

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To date, the existence of the plant inner membrane anion channel (PIMAC) has been shown only in potato mitochondria, but its physiological role remains unclear. In this study, by means of swelling experiments in K+ and ammonium salts, we characterize a PIMAC-like anion-conducting pathway in mitochondria from durum wheat (DWM), a monocotyledonous species phylogenetically far from potato. DWM were investigated since they possess a very active potassium channel (PmitoKATP), so implying a very active matching anion uniport pathway and, possibly, a coordinated function. As in potato mitochondria, the electrophoretic uptake of chloride and succinate was inhibited by matrix [H+], propranolol, and tributyltin, and was insensitive to Mg2+, N,N′-dicyclohexylcarbodiimide (DCCD) and mercurials, thus showing PIMAC's existence in DWM. PIMAC actively transports dicarboxylates, oxodicarboxylates, tricarboxylates and Pi. Interestingly, a novel mechanism of swelling in ammonium salts of isolated plant mitochondria is reported, based on electrophoretic anion uptake via PIMAC and ammonium uniport via PmitoKATP. PIMAC is inhibited by physiological compounds, such as ATP and free fatty acids, by high electrical membrane potential (ΔΨ), but not by acyl-CoAs or reactive oxygen species. PIMAC was found to cooperate with dicarboxylate carrier by allowing succinate uptake that triggers succinate/malate exchange in isolated DWM. Similar results were obtained using mitochondria from the dicotyledonous species topinambur, so suggesting generalization of results. We propose that PIMAC is normally inactive in vivo due to ATP and ΔΨ inhibition, but activation may occur in mitochondria de-energized by PmitoKATP (or other dissipative systems) to replace or integrate the operation of classical anion carriers.

Keywords: Anion transport; Durum wheat mitochondria; Inner membrane anion channel; Jerusalem artichoke mitochondria; Potassium channel

Journal Article.  9998 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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