SPPS Newsletter October 2007

Index of Issue II 2007

Transgenic Arabidopsis that turn red in the presence of explosives will be presented at the SPPS PhD conference. Photo by Henrik Freek.

A couple more speakers have been announced for the 5th biannual SPPS PhD conference that will take place January 24-27 2008 at Haslev Højskole 60 km south of Copenhagen. It is Professor Heribert Hirt from University of Vienna, Austria, who will deliver the keynote presentation on the topic Abiotic and Biotic Stress. Heribert Hirt makes extensive use of Arabidopsis mutants to investigate perception and transduction of stress signalling as well as programmed cell death and other stress related responses.

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Above: The fluorescent probe (black sphere) absorb a photon (blue) and moves to an exited state. When it returns to the stable ground state a photon (green) is released. In some cases, two low-energy photons (red) can excite a probe which subsequently emits a single high-energy photon (green). Below: Typical excitation and emission spectra for a fluorescent probe. From Vonesh et al (May 2006) IEEE Sig Proc Mag

Biologists have come to depend more and more on bioimaging as a tool to identify and locate specific proteins and molecules in their natural environment. With the recent development of probes and microscopes, biological processes can be monitored in real time in two or three dimensions. And observations can even be made non-invasively so a cellular process can be followed over an extended period of time.

Bioimaging relies on probes that are attached to proteins or other molecules of interest. These probes are fluorescent and as such emit light of a specific wavelength when they are excited by light of another – usually shorter – wavelength. Cells and their components are mainly transparent and the myriad of molecules within them are indistinguishable from each other in a normal microscope. But if the protein of interest lights up in bright green, it is easy to detect and distinguish from all other molecules in the cell.

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Carbohydrate signalling in e.g. symbiosis is studied by CARB. From www.carb.dk

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.

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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 here: Favre & Agosti (October 2007) Physiologia Plantarum 131: 263-272

Little is known about the evolutionary origin of mycorrhiza, the symbiotic relationship between plant and fungus. Arbuscular mychorriza (AM) helps 80% of all vascular plants in extracting phosphate and other nutrients from the soil and is believed to have been critical for land plant development. Now a team of mainly Swiss scientists have discovered that lyso-phosphatidylcholine act as a molecular signal that turn on mycorrhiza-specific genes in potato. The lysolipid also induced other mycorrhiza-specific genes in tomato and caused extracellular alkalinization, which is known to lead to alterations in gene expression.

Source: Drissner et al (12 October 2007) Science 318: 265-268

Rice is one of the world’s most important food crops, but despite the fact that yield has more than doubled in the last few decades, the cultivars need improvement in order to remain sustainable and nourishing. Pesticides and fertilizers are currently overused to secure the harvest, and problems with pests, diseases, drought and marginal land use are becoming increasingly more severe. Qifa Zhang from Huazhong Agricultural University in Wuhan, China has outlined a strategy for developing new ‘green super rice’. The genes for most of the desired traits are known and have been isolated, and they can eventually be combined in a single cultivar using marker-assisted breeding, transformation and hybrid production.

Source: Zhang (1 October 2007) PNAS doi:10.1073/pnas.0708013104