NEWS FROM
PHYSIOLOGIA PLANTARUM
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Published monthly on behalf of SPPS by Wiley-Blackwell.
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Tuned channels
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Coping with osmotic stress requires a plant to adjust both the water level and the salt concentration within its cells, and according to a new Chinese study these functions seem to be co-regulated. Scientists from Shanghai Institutes for Biological Sciences studied potassium and water channels in 3 weeks old rice seedlings. During water stress genes encoding both water channel and potassium channel proteins were downregulated, presumably in order to promote celluar water conservation. On the contrary, K+-starvation resulted in upregulation of the genes encoding both channels.
Read full article free: Liu et al (September 2006) Physiologia Plantarum 128: 58-69
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NEWS IN BRIEF
FROM OTHER JOURNALS
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Woody genetics
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Source: Tuskan et al (15 September 2006) Science 313: 1596-1604
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Amoeba offer clues to how plants arose
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Source: Yoon et al (5 September 2006) Current Biology 16: R670-R672
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Scandinavian research institute:
Göteborg University, Sweden
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The main building of Göteborg University is guarded by lions. Photo courtesy of Göteborg University.
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Göteborg is the second largest town in Sweden, but its university is the largest in the whole of Scandinavia. With 51.000 students, 5.221 employees, 8 faculties and 70 departments it is uniquely wide-ranging and offers the most comprehensive selection of courses in Sweden. The university dates back to 1891 and experienced rapid expansion during the 1950s and 1960s - increasing the number of students from only 500 to 21.000 in two decades.
Plant molecular biology, however, was not established as an independent subject until 2001. It is now part of the Department of Plant and Environmental Sciences, which also covers research in plant physiology, systematics, applied environmental science, ecology and the university's herbarium. The approximately 17 plant molecular biologists in Göteborg are using molecular, genetic, biochemical and physiological approaches to investigate biological processes in the model plants Arabidopsis and rice.
The team is divided into 4 research groups:- Molecular chaperones and proteases in photosynthetic organism
Professor Adrian K. Clarke - Membrane lipid trafficking within chloroplasts
Professor Anna Stina Sandelius - Protein trafficking into chloroplasts
Dr Henrik Aronsson - The plant innate immune system
Dr Mats Ellerström
Adrian Clarke and his colleagues study the turn-over of proteins by looking at chaperones and proteases. Generally speaking, chaperones promote stability while proteases cause degradation of proteins, but they also work together. E.g. chaperones can unfold a protein and expose a protease target site and thereby increase specificity and avoid inadvertent degradation of other cellular components.
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Knockout of Clp proteases causes chlorotic phenotypes. Photo from Clarke et al (2005) Physiol Plant 123: 406.
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Using knockout and antisense mutants of Arabidopsis, the research group has extensively investigated the large and diverse group of ATP-dependent caseinolytic proteases (Clp) found in chloroplasts. Many of these mutants are embryo lethal - stressing their developmental importance during development - while others cause chlorosis. In a recent study, a nuclear encoded subunit of a chloroplast Clp protease were shown to be essential for early development in Arabidopsis.
Chloroplasts are also the centre of interest for Anna Stina Sandelius. She is looking into how phospholipids in the tonoplast can serve as a phosphate reservoir that is being released upon P-starvation. In a recent publication her group showed that in phosphate-limited oat up to 70% of membrane phospholipids were replaced by digalactosyldiacylglycerol (DGDG), which is a sugar-containing lipid. In this way, bound phosphate was apparently made available for the plant.
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Chloroplasts are extensively investigated in Göteborg. From http://www.tqnyc.org
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Lipid composition of the membranes was reverted when phosphate was re-supplied, and Anna Stina Sandelius is now investigating how this lipid trafficking is regulated. Her research has indicated that a phospholipase D-type activity and a phosphatidic acid phosphatase are induced during phosphate starvation, and that the response seems to be both tissue and species specific and to depend on developmental stage.
Henrik Aronsson is studying import to the chloroplast of proteins involved in their development. One crucial step is the light-dependent reduction of protochlorophyllide to chlorophyllide, which is catalysed by a nuclear encoded NADPH-dependent oxidoreductase, POR. POR must be translocated over the chloroplast membranes, but how this happens is a matter of scientific debate. The team at Göteborg University works to resolve whether import of POR depends on its own substrate, protochlorophyllide, or if it uses the general translocation machinery.
Even Mats Ellerström has an interest in chloroplasts. Last year he discovered a DNA-binding protein, BnPEND, in Brassica napus that are involved in regulation of chloroplast gene expression and, when over-expressed, can block plastid development. His main focus, however, is on inducible disease resistance responses. By expressing avirulence proteins from Pseudomonas syringae using inducible promoters in Arabidopsis he has recently been able to demonstrate a phospholipase-dependent signalling system. Phospholipase inhibitors could block the resistance response, while addition of phospholipase caused defence-gene activation.
You can find more information about plant molecular biology at Göteborg University at the official website.
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