Plant Nucleotide Sugar Formation, Interconversion, and Salvage by Sugar Recycling*

Abstract

Nucleotide sugars are the universal sugar donors for the formation of polysaccharides, glycoproteins, proteoglycans, glycolipids, and glycosylated secondary metabolites. At least 100 genes encode proteins involved in the formation of nucleotide sugars. These nucleotide sugars are formed using the carbohydrate derived from photosynthesis, the sugar generated by hydrolyzing translocated sucrose, the sugars released from storage carbohydrates, the salvage of sugars from glycoproteins and glycolipids, the recycling of sugars released during primary and secondary cell wall restructuring, and the sugar generated during plant-microbe interactions. Here we emphasize the importance of the salvage of sugars released from glycans for the formation of nucleotide sugars. We also outline how recent studies combining biochemical, genetic, molecular and cellular approaches have led to an increased appreciation of the role nucleotide sugars in all aspects of plant growth and development. Nevertheless, our understanding of these pathways at the single cell level is far from complete.

Primary Metabolism during Biosynthesis of Secondary Wall Polymers of Protoxylem Vessel Elements

“…These observations suggest that GAP metabolism has important functions in the glycolysis pathway during protoxylem vessel element differentiation, probably involving the concentration of carbon sources within the glycolysis pathway to Fru-6-P by arresting glycolysis in the upstream steps of GAP. Fru-6-P is a key metabolite converted into NDP-sugar and/or connecting glycolysis with the pentose phosphate pathway (Bar-Peled and O'Neill, 2011;Roach et al, 2012). NDP-sugars are building units of cell wall polysaccharides; therefore, the activation of Fru-6-P biosynthesis is possibly connected to the activation of SCW formation during protoxylem vessel element differentiation.…”

The dehydratase ADT3 affects ROS homeostasis and cotyledon development

“…Also, the expression of proteins of starch and Suc metabolism, pentose and glucuronate interconversions, as well as amino sugar and nucleotide sugar metabolism is increased in the adt3-1 mutant. The enrichment of enzymes from these pathways provides a link between cell wall metabolism and central plant metabolism (Seifert, 2004;Bar-Peled and O'Neill, 2011).…”

UUAT1 Is a Golgi-Localized UDP-Uronic Acid Transporter That Modulates the Polysaccharide Composition of Arabidopsis Seed Mucilage

“…Most GTs are type-II membrane-bound proteins with a catalytic domain facing the Golgi lumen (Sterling et al, 2001;Wulff et al, 2000;Scheible and Pauly, 2004). However, most nucleotide sugars utilized by GTs are produced in the cytosol (Bar-Peled and O'Neill, 2011;Bonin et al, 1997;Seifert, 2004). Therefore, the Golgi membrane is a physical barrier blocking access to the active GT site.…”