Planta

, Volume 207, Issue 2, pp 163–171 | Cite as

Iodine uptake in Laminariales involves extracellular, haloperoxidase-mediated oxidation of iodide

  • F. C. Küpper
  • N. Schweigert
  • E. Ar Gall
  • J.-M. Legendre
  • H. Vilter
  • B. Kloareg
Article

Abstract.

Sporophytes of Laminaria digitata (L.) Lamour. were assayed for their content of accumulated iodine, which ranged from 0.4% of dry weight in adult plants up to 4.7% for young plantlets. Sporophyte tissue from Laminaria saccharina (L.) Lamour. and L. digitata took up iodide according to Michaelis-Menten kinetics. Hydrogen peroxide and various substances known to interfere with oxidative metabolism were shown to either inhibit or enhance the uptake of iodide, confirming that apoplastic oxidations play a key role in iodide uptake in Laminaria. Consistently, iodide uptake was triggered in L. saccharina protoplasts by incubation in the presence of hydrogen peroxide. Similarly, the uptake of iodide was enhanced in L. digitata gametophytes by addition of haloperoxidase, suggesting that this enzyme catalyses the oxidation of iodide by hydrogen peroxide and plays a key role in iodine uptake. Oxidative stress resulted in a marked efflux of the intracellular iodine. In both influx and efflux experiments, a marked proportion (10–30%) of the tracer was not accounted for, indicating volatilisation of iodine. The mechanism and possible functions of the accumulation of iodine by kelps are discussed.

Key words: Apoplastic oxidative metabolism Haloperoxidase Hydrogen peroxide Iodine Laminaria 

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Copyright information

© Springer-Verlag Berlin Heidelberg 1998

Authors and Affiliations

  • F. C. Küpper
    • 1
  • N. Schweigert
    • 1
  • E. Ar Gall
    • 1
  • J.-M. Legendre
    • 2
  • H. Vilter
    • 3
  • B. Kloareg
    • 1
  1. 1.Centre d'Etudes Océanologiques et de Biologie Marine, CNRS, UPR 9042, F-29682 Roscoff, Brittany, FranceFR
  2. 2.Service de Médecine Nucléaire, CHU Morvan, F-29200 Brest, Brittany, FranceFR
  3. 3.Zurmaiener Straße 16, D-54292 Trier, GermanyDE

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