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Research at NTNU CMB
Signal transduction regulated by RAC/ROP GTPases
Through our research on RAC/ROP GTPases at CMB we aim to map the function of these highly conserved molecular switches in plants. RAC/ROP proteins belong to the RAS superfamily of small GTPases and can be found in primitive eukaryots as well as in plants, fungi and animals. In eukaryotic cells, the Rho-family of small GTPases (RAC, RHO and Cdc42) has key functions in the initial steps of several signal transduction pathways. In Arabidopsis thaliana the Rho family consists of 11 RAC-like members and based on phylogenetic analyzes and protein comparisons we decided to call these proteins AtRACs Winge et al. 2000 . Plant RAC GTPases perform functions similar to RAC proteins found in other eukaryotic organisms, such as regulation of the actin cytoskeleton, polarized cell growth and host defence. However, they are also likely to regulate processes unique to plants. For an up-to-date review on AtRAC/ROP GTPases and WAVE mediated regulation of the cytoskeleton see Brembu et al. 2006.
Cellular- and molecular organisation and function of plant defence systems
Plants are challenged by predators, pest and pathogens. To fight back they have developed advanced cellular and chemical defence systems. These plant defence systems generate products that are the basis of many medicines and the natural products used for therapi. Many of these products are toxic in nature and a major reason why we only use a few plants for food production. The plant also needs to protect itself from the defence related compounds. Protection mechanisms may e.g be cellular separation of enzyme activities and substrates or tight control with factors affecting metabolism of the substrates/products. Since plant defence compounds often control the level of pest infestation and pathogen infection of plants they also have an economically important role in food production. Molecular biology and genomics now makes it possible to explore the importance of such defence systems and their important role for human and animal health. Our model system, the myrosinase-glucosinolate system, includes a complex enzyme system consisting of thioglucoside glucohydrolases (myrosinases), myrosinase binding proteins, myrosinase associated proteins, epithiospecifier proteins and nitrilases and more than 100 different thioglucoside (glucosinolate) substrates that are able to produce an array of products with biological function. These products have multiple biological activities. We are interested in how these systems are organised at a cellular and subcellular level, their function and the biological activities of the products as well as the potential to modify activities and concentration of products. The defence systems of plants are important for the interaction between plants and other living organisms. Together with Dr. John T. Rossiter and colleagues at Imperial College, UK, we have recently characterized a similar system in insects feeding on plants. The interest for our model system has increased dramatically the last few years and this field of research today includes research groups in plant sciences, medicine, chemistry, biochemistry, pharmacy and animal sciences.
References: Bones and Rossiter 1996, Bones and Rossiter 2006, Grubb and Abel 2006, Halkier and Gershenzon 2006.