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• Multiple abiotic stress tolerance and Systemic signalling in the plant pathogen response
  
  

  During their life, plants face a multitude of non-predictable and harmful environmental conditions, requiring them to promptly translate perceived stress signals into transcriptional re-programming and subsequent stress adaptation. Upon exposure to drought, osmotic, cold, UV and other abiotic adversities plants employ molecular signalling pathways that – astonishingly - partially overlap. 

  
  
  Fig. 1 Arabidopsis thaliana. Wild type (left) and genetically modified (right). Enhanced activation of a stress resistance gene slows down development

  With respect to biotic stresses, such as pathogen attack, a range of local defence responses are initiated that restrict further damage near the infection site. In addition, phloem-translocated (“systemic”) signals are released from the infection site and put non-infected tissue into a “primed” state which allows a more rapid and stronger response to subsequent attack. Despite its unquestionable role as a major survival strategy and the associated agricultural importance, systemic acquired resistance (SAR) and the molecular mechanisms leading to its establishment are still poorly understood. 

  
  Fig. 2 Arabidopsis-protoplasts (Cells whose cell wall has been removed) serve as tools for transient gene expression.

  By acting downstream of stress receptors and upstream of stress-dependent transcription factors, Mitogen-activated protein kinase (MAPK) cascades are key players in the early stress signal transduction. Yet, in vivo evidence for MAPK substrates is very limited. The Arabidopsis thaliana protein MAPK3 is rapidly activated by numerous abiotic and biotic stresses and thus presents a molecular node in early stress signalling.

  Employing the rich pools of bioinformatics prediction programmes, protein- and gene expression arrays, a substrate of the stress-activated MAPK3 was predicted (and subsequently confirmed). The correlation between this phosphoprotein and MAPK3 as well as the functional relevance of their interaction for the development of SAR are currently being investigated.

  The second protein of interest is a MAPK-targeted MYB transcription factor, which plays a role in the response to a variety of abiotic stresses, including drought, cold and osmotic stress. Phosphorylation-targeted sites in the MYB transcription factor have been identified. Transgenic plants ectopically expressing mutant phospho-mimicking variants of the protein are expected to display an altered stress tolerance. 

  
  Fig. 3 Phosphorylation of target proteins, visualized by autoradiography.

  Both hypothesised MAPK substrates are functionally characterised by means of in vitro and in vivo interaction assays, transient expression studies in protoplasts as well as in transgenic plants. Given the high homology of these two proteins across various plant species and the strong conservation of MAPK signalling mechanisms, the outcome of our studies is not only of interest for basic research, but it may also facilitate the engineering of multi-stress resistant crops. 

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Lange Nacht der Forschung	BOKU Top Stories http://www.lnf2012.at/index.php?option=com_jumi&fileid=7&Itemid=56&group_id=1100
Fascination of Plants Day	http://www.plantday12.eu/

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