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.