NEWS FROM
PHYSIOLOGIA PLANTARUM
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Published monthly on behalf of SPPS by Wiley-Blackwell.
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Arabidopsis get excited
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Action potentials, i.e. rapid and transient changes of the membrane potential that travel over long distances, are not unique to animals. Several plants exploit them for various purposes: capturing insects in the carnivorous Venus flytrap, rapid movement of leaves in Mimosa and triggering of a systemic response following injure in tomato. However, action potentials in plants have not been thoroughly studied due to the lack of a suitable and reproducible model system. Now Swiss scientists propose Arabidopsis thaliana as such a model. Excitation by electrodes in the distal part of the leaf caused reproducible action potentials that travelled down through the petiole at a speed of 1.2 mm/s.
Read full article free: Favre & Agosti (October 2007) Physiologia Plantarum 131: 263-272
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NEWS IN BRIEF
FROM OTHER JOURNALS
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Potatoes highlight the plant-fungi relationship
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Source: Drissner et al (12 October 2007) Science 318: 265-268
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Recipe for better and sustainable rice
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Source: Zhang (1 October 2007) PNAS doi:10.1073/pnas.0708013104
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Scandinavian research institute:
CARB - Centre for Carbohydrate Recognition and Signalling, Aarhus, Denmark
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Carbohydrate signalling in e.g. symbiosis is studied by CARB. From www.carb.dk
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Less than a year ago, CARB was announced as a new Centre of Excellence by the Danish National Research Foundation. CARB (Centre for Carbohydrate Recognition and Signalling) is headed by Professor Jens Stougaard at University of Aarhus, and most researchers from the new centre come from his group at the Department of Molecular Biology. However, Professor Knud Jørgen Jensen from University of Copenhagen (Denmark), Professor Herman Spaink from University of Leiden (The Netherlands) and Professor Clive Ronson from University of Otago (New Zealand) do also participate.
CARB seeks to elucidate the involvement of carbohydrates in interactions between cells and organisms, which frequently occur as part of pathogenesis, symbiosis and development. The approach taken is multidisciplinary and exploits state-of-the-art technologies like bioinformatics, genomics, proteomics, structural biology and nanobioscience to mention just a few. The model organisms of choice are zebrafish and the legume Lotus japonicus, which exhibit complex interactions with pathogenic and symbiotic microorganisms, respectively.
Such interactions are often controlled by polysaccharides and glycans attached to or secreted from the microbial cell wall, which are then recognized by receptors on the eukaryotic cell surface. By experimental manipulation of both the ligand and the receptor, CARB will attempt to characterize and compare carbohydrate signalling in the two model systems and to investigate how the signals are recognized and turned into a cellular response.
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Bacterial nod factors trigger the infection process and elicit nodule formation on the host plant roots. From www.glycoforum.gr.jp
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Jens Stougaard has pioneered research in the symbiotic relationship between legumes and the soil bacteria rhizobia for more than a decade. In a Nature paper from 1999, he reported the use of transposon-tagged Lotus japonicus mutants to identify the regulatory components of the formation of nitrogen-fixing root nodules that are characteristic of legumes. Rhizobia live in the soil and if they have the correct nod (nodulating) genes, they can enter a root hair of a legume and initiate symbiosis.
The plant respond by forming a nodule where the bacteria reside and fix atmospheric nitrogen in to ammonium, that can be utilized by the plant. In return, the bacteria receive carbohydrates, proteins and oxygen from the plant. The relationship is mutually beneficial and is of significant importance in agriculture, where nitrogen is the most commonly deficient nutrient and is supplied through fertilizers to a great extent.
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Legume mutants lacking a LysM receptor (c, d) cannot initiate nodule formation as the wild-type (a, b). From Radutolu et al (2003) Nature 425: 585
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A major focus of CARB is to characterize the plant-bound LysM domains of receptors that enable recognition of the bacterial symbiont. In another Nature paper from 2003, Jens Stougaard and his colleagues described how these peptidoglycan- and chitin-binding domains are required for perception of the rhizobial signal and the onset of the first physiological and cellular responses of the plant, which eventually lead to nodule formation.
A very recent publication in EMBO Journal demonstrates how LysM domains are critical for determination of the symbiotic host range in a number of legumes. As LysM domains are wide spread in both plants and animals, the researchers at CARB will compare the ligand-binding properties and signalling mechanisms of LysM containing receptors across the kingdoms.
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The zebrafish (Danio rerio) is an important model organism - worldwide and at CARB. From wikipedia.org
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Molecules similar to the lipochitinoligo-saccharides that are secreted by rhizobia and recognized by LysM domains also seem to be involved in the development of zebrafish. Herman Spaink, the Dutch participant of CARB, has previously shown that they have an important developmental role during embryogenesis and that their absence lead to severe defects in trunk and tail development.
The Danish National Research Foundation has supported CARB for a 5 year period running from 2007-2011.
You can find more information about CARB at the centre's official website.
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