Disentangling Sugar Signaling in Plants

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DISENTANGLING SUGAR SIGNALING IN PLANTS ABSTRACT Sugars like glucose and fructose power and control the development of all living organisms. In plants, multiple enzymes involved in sugar metabolism—namely HEXOKINASES (HXKs) and FRUCTOSE 1-6-BIPHOSPHATASES (FBPs)—also function as sensing and signaling hubs that regulate gene expression. Three major challenges hinder the understanding of the physiological role of these enzymes, not only in plants but in multicellular organisms at large. First, mutations of these enzymes result in pleiotropic effects that complicate the interpretation of organ and tissue-level phenotypes. Second, because they act jointly in metabolism and signaling, it is difficult to differentiate the contribution of individual enzymes to the ultimate phenotype. Lastly, methods to quantitatively monitor the activity of individual enzymes directly, non-destructively, with cellular resolution, and in planta are lacking. As a result, all direct targets of HXKs and FBPs regulation and their involvement in plant growth have not been elucidated. This MIRA project will use protein engineering, chemical screening, and synthetic biology to generate biomolecular tools that will allow the isolation, manipulation, and monitoring of the individual metabolic and signaling activities of HXKs and FBPs. The main goal of this project is to manipulate these enzymes' signaling functions without affecting the cells' metabolism and vice versa. Furthermore, all synthetic constructs will be deployed in a tissue-specific manner to differentiate systemic and cell-autonomous effects. The chosen model system will be the primary root of Arabidopsis thaliana, an organ that is anatomically simple, genetically tractable, chemically accessible, and amicable to confocal microscopy.