Influence of GSK-based signaling on the metabolic web

Plant metabolism is highly flexible. It is adjusted during development and in response to the environment. Environmental cues have to be sensed and transduced via signal transduction pathways to modulate the activity state of metabolic enzymes. Mass spectral-based analysis allows to monitor metabolic levels and fluxes in a large scale highlighting the dynamics of plant metabolism in response to changing conditions. Various biochemical and molecular approaches as well as studies on transgenic and mutant plants identified protein kinases as key components governing cellular signaling. Despite of our knowledge on these processes our understanding of the connectivity between signal transduction and metabolic adaptation is scarce. The family of glycogen synthase kinase 3/shaggy-like kinases (GSKs) are implicated in mediating different extracellular stimuli to various physiological responses. The group of C. Jonak provided evidence that distinct GSKs might play an important role in plant stress signaling. For example, MsK4 appears as a positive regulator of the high salinity response. MsK4 kinase activity is rapidly increasing upon high salt stress and overexpression of MsK4 enhances the tolerance to high salinity and modulates the metabolite content. The proposed project will use metabolic profiling of Arabidopsis plants with altered ASK (Arabidopsis GSK) activity levels. Changes in the abundance of metabolic compounds including those in glutathione and ascorbate levels by gas chromatography-mass spectrometry and high performance liquid chromatography will be determined in lines with enhanced ASK activity and in mutant lines disrupted in a specific ASK and compared to wild type plants. This will be the first comprehensive study on the influence of a kinase family on the metabolism of plants and promises to provide an insight how cellular signaling is linked to metabolic flexibility.