NEWS FROM
PHYSIOLOGIA PLANTARUM
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Published monthly on behalf of SPPS by Wiley-Blackwell.
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Resurrection from aparent death
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Being adopted to the hot and dry summers of the Balkan Peninsula, Ramonda serbica can withstand several weeks of severe dehydration and resurrect from apparent death. In a study performed by Italian and Yugoslavian researchers from the universities of Pisa and Belgrade, phenolics were shown to play a critical role in the scavenging of free radicals during dehydration and subsequent rehydration. Phenolic acids, primarily chlorogenic acid which is known to be a very active antioxidant, are stored in unusually high levels prior to dehydration, but become depleted as relative water content drops to less than 5%. The authors suggest that Ramonda serbica utilizes a peroxide/phenolics/ascorbate system for detoxification of hydrogen peroxide.
Read full article free: Sgherri et al (December 2004) Physiologia Plantarum 122: 478-485
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NEWS IN BRIEF
FROM OTHER JOURNALS
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Ancient brew of rice, honey and fruit
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Source: McGovern et al (21 December 2004) PNAS 101: 17593-17598
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Rubisco makes seedfilling go on oiled wheels
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Source: Schwender et al (9 December 2004) Nature 432: 779-782
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Scandinavian research institute:
Plant Stress Group, University of Helsinki
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The Plant Stress Group is situated in the Viikki Campus that houses research and teaching facilities for 6,000 students and 1,500 teachers. Photo by Eero Roine & Ida Pimenoff
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Ozone not only gives the forest a clean and fresh smell, it is also an air pollutant that mimics plant-pathogen interactions and induce cell death in plants.
This is being exploited at the Plant Stress Group in Helsinki, where they have set up a system for the controlled exposure of plants to ozone. In combination with a large collection of Arabidopsis mutants this is a powerful approach to study the several signal transduction pathways that regulate plant responses to biotic and abiotic stress.
The Plant Stress Group is part of the Department of Biological and Environmental Sciences at University of Helsinki. The Department was formed in the beginning of 2004 by the fusion of three institutes and belongs to the Faculty of Biosciences. It resides at the Viikki Campus together with the Faculty of Agriculture and Forestry, and the Faculty of Pharmacy.
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Professor Jaakko Kangasjärvi is head of the Plant Stress Group. Photo courtesy of Jaakko Kangasjärvi.
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The reorganization has brought more than 12 research groups in plant molecular biology together to one location, and even though they are at different departments and faculties they do work together in several aspects. Interactions between the groups are very frequent and informal and includes sharing of equipment and techniques.
Professor Jaakko Kangasjärvi, Head of the Plant Stress Group, however, points out that eight of the plant groups - including his own - have joined to form a Center of Excellence funded by the Academy of Finland. And he believes that this level of organization gives the individual research groups an excellent opportunity to focus their efforts.
And the research at the Plant Stress Group is indeed very focused. One might argue that the group studies the molecular and biochemical mechanisms of pathogen defence, but nonetheless their laboratory is an absolute pathogen-free zone. Pathogens are difficult to control and their ability to trigger the plants defence systems can be unreliable. But put the plant in a growth chamber where it is subjected to computer controlled levels of ozone, and you closely mimic the plant's natural and immediate response to pathogens - namely the production of reactive oxygen species that activates a network of signalling cascades.
Differential expression of genes after ozone exposure is studied by means of DNA micro- and macroarrays as well as large cDNA and EST collections. This enables the researchers to identify novel genes involved in the signal transduction pathway, and their specific functions are subsequently analyzed using mutants and T-DNA insertion lines. Not only Arabidopsis but also birch and Populus are used for these genomic analysis.
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Mutant studies show how ethylene and jasmonic acid modulates ozone-induced cell death. Photo courtesy of Jaakko Kangasjärvi.
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In combination with such genomic tools, the ozone fumigation system allows The Plant Stress Group to carefully study the cascade of physiological and molecular responses elicited by reactive oxygen species during stress. In a recent publication in Plant Journal, Jaakko Kangasjärvi and his colleagues show at the molecular level how ethylene and jasmonic acid have opposite effects on ozone-induced cell death.
By comparing stress responses from mutants defective in several different signalling pathways they demonstrated that cell death was stimulated by ethylene and suppressed by jasmonic acid, and that regulated expression of genes in either pathway controlled propagation of cell death.
Subsequent work, published recently in Plant Cell, indicate that one of these mutants, rcd1, displays several pleiotropic phenotypes related to hormonal responses. The results suggest that the defective gene plays a key role in the hormonal regulation of stress-responsive signal transduction pathways by an as yet unknown biochemical mechanism. And this is a lead that Jaakko Kangasjärvi and his colleagues want to follow in the future.
You can find more information about the Plant Stress Group on its official website.
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