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Ectocarpus siliculosus

Ectocarpus siliculosus. Filamentous, cosmopolitan brown alga – mostly from temperate seas One of the best-studied seaweeds The first fully-sequenced multicellular alga – ongoing genome annotation > 300 fully-characterized strains in public-domain culture collections (CCAP, KU-MACC).

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Ectocarpus siliculosus

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  1. Ectocarpus siliculosus • Filamentous, cosmopolitan brown alga – mostly from temperate seas • One of the best-studied seaweeds • The first fully-sequenced multicellular alga – ongoing genome annotation • > 300 fully-characterized strains in public-domain culture collections (CCAP, KU-MACC)

  2. So what about Ectocarpus? • Ectocarpus accumulates iodine, but at much lower levels than Laminaria (data from Roscoff & Vernaison) • Genome annotation has revealed the presence of one vanadium haloperoxidase gene • X-ray absorption spectroscopy using synchrotron radiation (XAS) on Ectocarpus

  3. Iodine K-edge XAS of Ectocarpus siliculosus • Like Laminaria, Ectocarpus accumulates iodine as iodide!

  4. Iodine metabolism in Ectocarpus • At present probably more questions than answers! • Does iodide have an apoplastic antioxidant function in Ectocarpus? • What does the genome tell us about antioxidant systems? • Does Ectocarpus produce iodinated / halogenated metabolites, are there iodo-/halocarbons? • Ongoing work - NERC SOLAS grant to Lucy J. Carpenter (York) and FCK

  5. Outlook and open questions • Mechanism of cell wall / apoplastic accumulation, storage of iodide? • How does the mobilization upon oxidative stress work? • Giant kelp / Macrocystis?

  6. So what about Greece and the Mediterranean Sea? • Very little is known about halogen fluxes in Mediterranean coastal systems! • In particular, molecular iodine and halocarbon emissions from Mediterranean seaweeds are seriously understudied

  7. So what about Greece and the Mediterranean Sea? • Some tropical/Mediterranean seaweeds are known to be strong iodine accumulators:Asparagopsis taxiformis (Rhodophyta) • Other candidates (known for strong halogen metabolism, albeit not iodine accumulation): Rhodophyta - Gracilaria sp., Ceramium sp., Dasya sp., Laurencia sp.Phaeophyta – Ectocarpales, Fucales (Sargassum sp.) • Deep-water kelp (Laminariales)?

  8. Deep-water kelp in the Mediterranean Sea • Laminaria rodriguezii, mainly known from western / central Mediterranean • Not known from Greece so far – lack of exploration of relevant depth range (> 50 m)

  9. Deep-water kelp forests in the tropics: An analogy to the Mediterranean Sea? Graham et al., 2007: Deep-water kelp refugia as potential hotspots of tropical marine diversity and productivity.- PNAS 104 (42), 16576-80

  10. Deep-water kelp in the Mediterranean Sea • What are the implications for marine and atmospheric halogen chemistry in the region?

  11. A place where you can smell the tide level… Roscoff, Brittany, France

  12. Acknowledgements • -- Peter M.H. Kroneck (University of Konstanz, Germany) • -- Sonja Woitsch, Markus Weiller (dto.) • -- Lucy J. Carpenter and Carl Palmer (University of York, UK) • -- Gordon McFiggans (University of Manchester, UK) • -- Philippe Potin (CNRS, Roscoff, France) • - Martin Feiters (University of Nijmegen, • The Netherlands) • - Wolfram Meyer-Klaucke and Gerd Wellenreuther (European Molecular Biology Laboratory, Hamburg, Germany) • - Eva M. Boneberg (Biotechnologie Institut Thurgau, Switzerland, formerly at University of Konstanz) • - Alison Butler (University of California, Santa Barbara, USA) • - George Luther & Tim Waite (University of Delaware, Lewes, USA) • - Rafael Abela & Daniel Grolimund (Swiss Light Source, Paul Scherrer Institute, Villigen, Switzerland)

  13. Thank you. Dunstaffnage Marine Laboratory, Oban, Argyll / West Highlands, Scotland

  14. Reserve slides follow

  15. What makes iodide a suitable antioxidant? Thermodynamics

  16. What makes iodide a suitable antioxidant? Thermodynamics

  17. What makes iodide a suitable antioxidant? Kinetics Compound k12 (M-1 s-1) O3 reactions with I- 1.2 x 109 Br- 2.48 x 102 Cl- < 3 x 10-3 Ascorbate 4.8 x 107 Glutathione 2.5 x 106 Singlet oxygen (1O2) reactions with I- 1 x 108 (aprotic solvents) 8.7 x 105 (pH ~ 7) Br- 1.0 x 103 Cl- 1.0 x 103 Ascorbate 8.3 x 106 Glutathione 2.4 x 106 (in D2O, 310 K, pD = 7.4)

  18. What makes iodide a suitable antioxidant? Kinetics Compound k12 (M-1 s-1) OH radical (OH) reactions with I- 1.2 x 1010 Ascorbate 1.1 x 1010 Glutathione 1.3 x 1010 (pH = 5.5) Dimethyl sulfoniopropionate 3 x 108 Dimethyl sulfide 1.9 x 1010 Dimethyl sulfoxide 6.6 x 109 Superoxide (O2-) reactions with I3- 1 x 108 (no data available for I-) Ascorbate 2.7 x 105 (pH= 7.4) Glutathione 2.4 x 105 (pH= 7.8)

  19. What makes iodide a suitable antioxidant? Kinetics Compound k12 (M-1 s-1) Hydrogen peroxide (H2O2) reactions with I- 0.69 Br- 2.3 x 10-5 Cl- 1.1 x 10-7 Ascorbate 2 x 100 Glutathione 2 – 20 x 100 Glutathione peroxidase 6 x 107

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