Presentation on theme: "Ectocarpus siliculosus Filamentous, cosmopolitan brown alga – mostly from temperate seas One of the best-studied seaweeds The first fully-sequenced multicellular."— Presentation transcript:
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)
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
Iodine K-edge XAS of Ectocarpus siliculosus Like Laminaria, Ectocarpus accumulates iodine as iodide!
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
Outlook and open questions Mechanism of cell wall / apoplastic accumulation, storage of iodide? How does the mobilization upon oxidative stress work? Giant kelp / Macrocystis?
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
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)?
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)
Graham et al., 2007: Deep-water kelp refugia as potential hotspots of tropical marine diversity and productivity.- PNAS 104 (42), Deep-water kelp forests in the tropics: An analogy to the Mediterranean Sea?
Deep-water kelp in the Mediterranean Sea What are the implications for marine and atmospheric halogen chemistry in the region?
Roscoff, Brittany, France A place where you can smell the tide level…
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)
What makes iodide a suitable antioxidant? Cl - Br - I-I- One-electron transfer per X - G R (kJ mol -1 ) X O 2 [X] + O X - + OH (g) [X] + OH X - + OH (aq) [X] + OH X O 2 [X] + O X - + H 2 O 2 [X] + OH + OH X - + H + + HO 2 [X] + H 2 O X - + O 3 [X] + O Thermodynamics
What makes iodide a suitable antioxidant? Cl - Br - I-I- Two-electron transfer per X - G R (kJ mol -1 ) 2 X - + H + + O 3 X 2 + O 2 + OH X - + H + + O 3 HOX + O X - + H + + 1O 2 + H 2 O HOX + H 2 O X - + 2H + + 1O 2 X 2 + H 2 O X - + H 2 O 2 HOX + OH X H + + H 2 O 2 X H 2 O Thermodynamics
What makes iodide a suitable antioxidant? Kinetics Compoundk 12 (M -1 s -1 ) O 3 reactions with I x 10 9 Br x 10 2 Cl - < 3 x Ascorbate4.8 x 10 7 Glutathione2.5 x 10 6 Singlet oxygen ( 1 O 2 ) reactions with I - 1 x 10 8 (aprotic solvents) 8.7 x 10 5 (pH ~ 7) Br x 10 3 Cl x 10 3 Ascorbate8.3 x 10 6 Glutathione2.4 x 10 6 (in D 2 O, 310 K, pD = 7.4)
What makes iodide a suitable antioxidant? Kinetics Compoundk 12 (M -1 s -1 ) OH radical ( OH) reactions with I x Ascorbate1.1 x Glutathione1.3 x (pH = 5.5) Dimethyl sulfoniopropionate3 x 10 8 Dimethyl sulfide1.9 x Dimethyl sulfoxide6.6 x 10 9 Superoxide (O 2 - ) reactions with I x 10 8 (no data available for I - ) Ascorbate2.7 x 10 5 (pH= 7.4) Glutathione2.4 x 10 5 (pH= 7.8)
What makes iodide a suitable antioxidant? Kinetics Compoundk 12 (M -1 s -1 ) Hydrogen peroxide (H 2 O 2 ) reactions with I Br x Cl x Ascorbate2 x 10 0 Glutathione2 – 20 x 10 0 Glutathione peroxidase 6 x 10 7