Posttranslational regulatory modules of carbon partitioning and allocation

Plants as sessile organisms are able to rapidly adapt to altering carbon availability throughout the diurnal cycle. Thereby, allocation of resources to growing sink organs involving membrane transporters is tightly integrated with metabolic and storage functions. This precise regulation requires tight and integrated control of metabolic activities and membrane transport. In the past years, phosphorylation sites and their dynamics of proteins in central carbon and sucrose metabolism as well as for respective transport were identified, but existing knowledge about the role of these modifications in modulation of metabolism, storage and transport is still limited. The major aim of this project is to gain further detailed insights into the role of protein phosphorylation in context of fluctuations in sucrose availability from extracellular or intracellular sources. In the proposed experiments, we will use different mutants with altered intrinsic sucrose status. We aim at (i) quantitatively monitoring protein phosphorylation of key proteins with sucrose-related responses in targeted assays under conditions of different external and internal sucrose availability and relate it to protein activities and carbohydrate content, (ii) studying subcompartmental distribution of membrane proteins in the respective mutants under different sucrose status, and (iii) verifying selected sucrose-related kinase-substrate relationships. Overall, the project will gain novel insights into on how plants use posttranslational regulation to integratedly respond to different requirements for carbon usage under rapidly changing external conditions.