Drough stress signalling

Drought is a major environmental constraint for plant growth and development and limits agronomical yield. Plants have evolved integrated signalling systems to delicately coordinate physiological responses to water shortage. Protein phosphorylation is central to signal transduction pathways although the immediate targets of kinases often remain elusive. We have provided evidence that an Arabidopsis GSK3/shaggy-like kinase (ASK) is important for tolerance to osmotic stress. Consistent with this, we found that drought induces the in vivo protein kinase activity of ASK. Furthermore, we have identified potential ASK interaction partners involved in stress signalling and regulation of gene expression. To unravel novel molecular mechanisms in drought stress signalling and adaptation to dry conditions we propose: (1) to analyse the regulation of ASK activity at the molecular level, (2) to position ASK within the signal transduction network, (3) to ascertain and functionally characterize targets of ASK in vivo, and (4) to study the impact of ASK on gene expression. We seek to address these tasks in Arabidopsis thaliana in a comprehensive approach combining physiological, molecular and biochemical methods with mutants. We expect to unravel basic mechanisms of ASK-based stress signalling regulating adaptation capacity to drought.

A key question in biology is how organisms adjust to adverse environmental conditions. As sessile organisms, environmental stresses, such as drought and high soil salinity, are major environmental constraints for plant growth and development and negatively affect agricultural productivity. A detailed knowledge of the mechanism of plant stress responses is therefore vital for sustainable agriculture in a changing environment. Protein kinases are key players for stress acclimation. Within the framework of this project, we have characterized a protein kinase as a novel regulator of stress tolerance. Protein kinases are important in adjusting gene expression to environmental changes. We provide strong evidence that the stress-related protein kinase interacts with chromatin components. Interestingly, the protein kinase interacts with and phosphorylates a novel plant chromatin-associated protein. A combination of global approaches with detailed biochemical, molecular and genetic analyses indicate that this protein is a chromatin architectural protein capable of modulating DNA topology, DNA accessibility and gene expression. Furthermore, we show that functional levels of the chromatin-associated protein are crucial for stress tolerance. The discovery of the interaction between the stress-related protein kinase and the novel plant chromatin-associated protein advances our knowledge of how stress signalling is linked to the chromatin and opens up exciting new avenues for future studies on plant chromatin organization and regulation.