Channeling sugar substrates into specific cell wall products through different nucleotide sugar transporters

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All plant cells are surrounded by a cell wall: a polysaccharide-based extracellular matrix that provides mechanical support and protection to plant cells. Plant cell walls are also vast renewable bioresources, supplying dietary fibre; materials like cotton, linen, paper, and wood; and feedstocks for biomaterials and biofuels. Activated sugars, called nucleotide sugars, are the "building blocks" of all cell wall polysaccharides. Most of nucleotide sugars are made in the cytosol and must be transported into the Golgi apparatus via transporters to supply the enzymes that assemble polysaccharides inside the Golgi. The Ebert lab has characterized six of these transporters (URGT1-6) that are required for transport of activated rhamnose and galactose into the Golgi apparatus for polysaccharide synthesis. We hypothesize that these URGTs may be localized to different membrane compartments (cisternae) of the Golgi, where they may supply substrates for synthesis of different cell wall polysaccharides. The McFarlane lab has established several techniques for high-resolution sub-Golgi localization of both proteins and polysaccharides and we propose to apply these approaches to the URGT family. Through student exchanges and collaborative experiments, this proposal aims to determine whether the different URGTs are localized to different Golgi compartments and how this impacts cell wall polysaccharide synthesis. Understanding the roles that each of these URGTs play in transporting the building blocks of cell wall synthesis into the Golgi can improve our understanding of the organization of polysaccharide synthesis within the Golgi apparatus may open new avenues for fine-tuning cell wall synthesis for biotechnological and agricultural applications.