The 9th International Sulfur Workshop was held at Schloss Reinach in Freiburg-Munzingen, Germany, and attracted close to 100 academia participants from 16 different countries. Young researchers were almost 50% of the total participants. The workshop was organized by the kongress & komminikation gGmbH in Freiburg and gathered 36 oral speakers and more than 40 posters presenters from all over the world. It was held at the 25th anniversary of the workshop series on “Sulfur in Plants” (see also: Plant Sulfur Network).
Connecting Physiologists, Molecular Biologists and Ecologists for the First Time
This workshop series started in 1989 and initially was focused on the physiology and biochemistry of sulfur in plants, later also on the molecular physiology of sulfur and on sulfur in agriculture. Upon preparation of the 9th International Sulfur Workshop it was recognized that sulfur in the environment is not restricted to its significance in the defense of abiotic and biotic stresses, but also includes the interaction of plants with other biota at the ecosystem level and in the biogeochemical sulfur cycle. Therefore, for the first time in the workshop series, the 9th International Sulfur Workshop made an effort to get a closer connection between scientists working in different disciplines on sulfur in biology.
Accordingly, the program covered a broad spectrum of topics ranging from the evolution and biogeochemistry of sulfur via biochemistry and genomics of sulfur metabolism in bacteria and fungi, to sulfur assimilation, transport and signalling in plants and sulfur nutrition in agro-ecosystems. The workshop was generously supported by Agrisera, CLF Plant Climatics, Deutsche Botanische Gesellschaft (DBG), Deutsche Forschungsgemeinschaft (DFG), Elsevier, Journal of Plant Physiology, KWS, and Plant Biology. By the Deutsche Botanische Gesellschaft, the keynote lectures of four young researchers were selected and supported: Meike Burow (Denmark): Cross-talk between glucosinolate biosynthesis and timing of flowering in Arabidopsis; Ann Cuypers (Belgium): Phytoremediation of metal-contaminated soils: essential role of thiols in chelation and detoxification; Robert Hänsch (Germany) Oxidfative and reductive detoxification of SO2; and Markus Wirtz (Germany): The cysteine synthase complex is the sensor of the sulfur availability in higher plants. A Young Scientist Award, sponsored by the Journal of Plant Physiology, was awarded to Kai Xun Chan (Australian National University, Canberra, Australia) for his work on stress retrograde signaling from secondary sulfur metabolism.
The workshop was opened by the Vice-Rector of the University of Freiburg, Prof. Dr. Gunter Neuhaus. Being a plant biologist by himself, he focused on the change of research on sulfur in plants during the past 25 years.
Evolution and Biogeochemistry of Sulfur Metabolism
The first session of the workshop was dedicated to the evolution and biogeochemistry of sulfur metabolism. James Farquhar (Department of Geology and ESSIC, University of Maryland College Park, Maryland, USA) reported about the use of sulfur isotopic signatures from well-dated sedimentary successions to identify the evolution of sulfur metabolism in earth history with special emphasis on terrestrial ecosystems. This was extended by the keynote of Timothy Ferdelman (Max Planck Institute for Marine Microbiology, Bremen, Germany) to marine sediments, where the sulfur cycle exerts a major control on the redox state of the ocean and, as a consequence, also of the atmosphere. This new and exciting addition to the areas of sulfur research covered by the workshop series was very well received by the participants.
Sulfur in Bacteria and Fungi
In the session on physiology, biochemistry and genomics of sulfur in bacteria and fungi, Christine Dahl (Institute for Microbiology and Biotechnology, University of Bonn, Bonn, Germany) focused on the dual role of sulfur metabolism of bacteria in (a) sulfur assimilation and its incorporation into organic compounds and (b) the use of sulfur as donor and acceptor for dissimilatory energy conserving electron transport. The large body of studies on the model yeast Saccaromyces cerevisiae was extended to the diversity of sulfur metabolism in hemiascomycetes yeasts by the contribution of Jean-Marie Beckerich (UMS MICALIS, INRA, AgroParisTech, Thiverval Grignon, France). The majority of the workshop participants being plant biologists learnt a lot from these contributions on microbial sulfur metabolism as new addition to the workshop series on sulfur in plants.
Sulfur in Higher Plants
The subsequent sessions all dealt with sulfur in higher plants. The session on regulation of sulfur assimilation and partitioning in plants underlined the role of the cysteine synthase complex as sensor of sulfur availability in the keynote by Markus Wirtz (Centre for Organismal Studies, Plant Molecular Biology, University of Heidelberg, Heidelberg, Germany) and the partitioning of sulfur between primary and secondary metabolism in the keynote by Stanislav Kopriva (Institute of Botany, Universty of Cologne, Cologne, Germany).The multitude of membrane transport processes of sulfur compounds in different cells and tissues was addressed by Hideki Takahashi (Michigan State University, Department of Biochemistry, East Lansing, USA). The significance of these processes for long-distance transport of sulfur and its root-to-shoot cycling in plants was outlined by Cornelia Herschbach (Institute of Forest Sciences, University of Freiburg, Freiburg, Germany).
Sulfur in Redox Regulation
The progress on the role sulfur in redox regulation of enzyme activities, growth and development of plants was addressed in two keynote lectures. Christine Foyer (Centre for Plant Sciences, Faculty of Biological Sciences, University of Leeds, Leeds, UK) reported about the numerous functions of the sulfur-containing tripeptide glutathione in different cellular compartments from the chloroplast to the nucleus. Nicolas Rouhier (Faculty of Sciences and Technologies, University of Lorraine-INRA, Vandoeuvre.les-Nancy, France) reported about the roles of glutaredoxins in the reduction of disulfide bonds and the binding of iron-sulfur (Fe-S) clusters. The signaling function of sulfur with special emphasis on H2S, recognized only recently as a signaling molecule, was addressed by John Hancock (University of West England, Bristol, UK). The role of sulfur in biotic interactions was discussed by Meike Burow (University of Copenhagen, Copenhagen, Denmark) with special emphasis on the cross-talk between the biosynthesis of glucosinolates, as defense against herbivores and pathogens, and the timing of flowering, again a very recent development in research on sulfur in plants.
Sulfur metabolism under Abiotic Constrains
Sulfur metabolism under abiotic constrains was covered by new insides into oxidative and reductive detoxification of SO2 in the contribution of Robert Hänsch (Institute for Plant Biology, Technical University of Braunschweig, Braunschweig, Germany) and the role of sulfur in plant programmed cell death and stress responses by Laura de Gara (Campus Bio-Medico, University of Rome, Rome, Italy). In the final session on sulfur nutrition in agro-ecosystems, the interaction of sulfur and nitrogen nutrition and its significance for grain quality was addressed by Karl Mühling (Institute of Plant Nutrition and Soil Science, Kiel University, Kiel, Germany). Stefania Astolfi (University of Tuscia, Viterbo, Italy) discussed the interaction of sulfur and iron limitation in plant growth and development.
A significant part of the workshop was devoted to poster sessions, partially combined with food and drinks. Thus, plenty of time and space was available for discussions around and beyond posters in the poster room and the courtyard of Schloss Reinach in order to support the exchange of ideas and to set up new collaborations.
Conclusion
The feedback from the conference attendances was extremely positive, on the high quality of the program, the presentations, the workshop organization including the social program, and the workshop venue. Apparently, the participants greatly enjoyed the chance to meet like-minded people from different disciplines and countries, the opportunity to network and to learn from each another, and the joint exploitation of new ideas. All scheduled speakers managed to connect their perspectives and data into a truly convergent exchange. The beautiful surroundings of Schloss Reinach and the City of Freiburg in Germany and France turned out to be just the right place for the workshop, bringing together diverse traditions in an international atmosphere.
Next Meeting
The 10th Jubilee Plant Sulfur Workshop, will be held on September 2nd - 5th, 2015 in Goslar, Germany, and will be devoted to analyzing the progress made on sulfur metabolism in plants since the 1st sulfur workshop in Groningen, The Netherlands in 1989.
Report from Prof. Dr. Heinz Rennenberg, Chair of Tree Biology, University of Freiburg, Germany
in May 2014