Plant salt stress tolerance and oxidative signalling

High soil salinity is a major environmental constraint on plant growth and development in numerous places in the world, resulting in large reductions in agronomic yield. Plants have evolved mechanisms to develop tolerance to environmental stresses. These mechanisms include protein phosphorylation- and reactive oxygen species (ROS)- mediated signalling. Increased levels of ROS are produced when plants are challenged by stress. ROS are crucial for signal transduction (cellular information transfer) but, when accumulating to excess levels, can also induce oxidative stress and damage cells. Stress-induced protein phosphorylation rapidly alters the function of its target protein(s) which are often involved in signal transduction and physiological responses. Recent studies have significantly advanced our knowledge of high salinity stress signalling. Yet, our understanding of the molecular mechanisms behind the signal transduction resulting in salt-stress tolerance is still limited. The Arabidopsis protein kinase ASKa has recently been identified as an important regulator of salt stress tolerance by the lab of C. Jonak. ASKa is involved in maintaining the cellular redox balance and in detoxifying excess levels of ROS under salt stress conditions. Based on recent data showing that ROS induce ASKa activity, the proposed project seeks to investigate the interaction between ROS signalling and ASKa. The project will investigate the mechanism(s) by which ROS regulates the activity of ASKa and will study the role of ASKa in oxidative stress signalling and tolerance. Furthermore, this project will determine whether ASKa is involved in mediating tolerance to other types of abiotic stress, such as drought, heat, or freezing. To accomplish this, genetic, molecular, and biochemical approaches will be combined with physiological studies in the model plant Arabidopsis thaliana. Overall, this comprehensive study on the interaction between ROS signalling, ASKa, and redox homeostasis will significantly increase our understanding of the basic mechanisms underlying salt stress signalling and tolerance.

Adverse environmental conditions increasingly challenge plant growth and development. The results of the project provide evidence that metabolic plasticity facilitates the adaptability of plants to different environmental conditions and contributes to stress tolerance and yield stability in challenging environments. Starting from studies on stress response pathways of the model plant Arabidopsis thaliana, the old European oilseed crop Camelina sativa, which is closely related to Arabidopsis, was investigated. Camelina is a versatile high-value food, feed, and industrial oil crop that can adapt to a wide range of climates and is considered naturally resilient. Eight camelina lines comprising cultivars and landraces from different geographic regions were characterized for important growth parameters and agricultural traits. Central carbohydrate metabolism is strongly associated with plant growth and development and its adaptation is vital for adjustment and maintenance of growth under stress conditions. Evaluation of 20 key enzymes of central carbohydrate metabolism revealed specific activity signatures in leaves and reproductive organs during seed development. Different lines showed distinct enzyme activity patterns which were associated with agronomic parameters/yield characteristics. Interestingly, effects of selection were visible on the level of enzyme signatures consistent with the selection history. Analysis of the different camelina lines for their tolerance to salt stress, antioxidant capacity, and response of central carbohydrate metabolism to salinity showed a better yield stability for naturally adapted landraces compared modern commercial lines. Mild salt stress led to changes in the activity of some key carbohydrate metabolic enzymes, with yield-stable lines showing different patterns of regulation than lines more affected by salt stress indicating that enzymatic plasticity contributes to plant adaptability to different environmental conditions increasing stress tolerance. Plasticity of central carbohydrate metabolism, which provides energy for successful stress acclimatization, therefore represents an interesting opportunity to stabilize crop yield under stress conditions. Enzyme activity signatures can be used to better understand the metabolic plasticity of different plant lines (genotypes) and identify suitable candidates for plant breeding to ensure agricultural production under changing climatic conditions.