Presentation on theme: "Ectocarpus siliculosus"— Presentation transcript:
1 Ectocarpus siliculosus Filamentous, cosmopolitan brown alga – mostly from temperate seasOne of the best-studied seaweedsThe 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 geneX-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 MediterraneanNot 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),
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)
17 What makes iodide a suitable antioxidant? KineticsCompound k12 (M-1 s-1)O3 reactions withI x 109Br x 102Cl- < 3 x 10-3Ascorbate x 107Glutathione x 106Singlet oxygen (1O2) reactions withI x (aprotic solvents)8.7 x 105 (pH ~ 7)Br x 103Cl x 103Ascorbate x 106Glutathione x (in D2O, 310 K, pD = 7.4)
18 What makes iodide a suitable antioxidant? KineticsCompound k12 (M-1 s-1)OH radical (OH) reactions withI x 1010Ascorbate x 1010Glutathione x (pH = 5.5)Dimethyl sulfoniopropionate 3 x 108Dimethyl sulfide x 1010Dimethyl sulfoxide 6.6 x 109Superoxide (O2-) reactions withI x (no data available for I-)Ascorbate x (pH= 7.4)Glutathione x (pH= 7.8)
19 What makes iodide a suitable antioxidant? KineticsCompound k12 (M-1 s-1)Hydrogen peroxide (H2O2) reactions withIBr x 10-5Cl x 10-7Ascorbate 2 x 100Glutathione 2 – 20 x 100Glutathione peroxidase 6 x 107