Figure 7.

Metabolic labeling. (A) Principle of metabolic labeling or click chemistry-based tracking of polysaccharides in plants. Functionalized monosaccharides are loaded into plants. After entering the cell, they are incorporated by biosynthetic pathways pertinent to the respective glycan. The tracking analysis is enabled by a click reaction to a fluorophore containing a compatible reactive group. (B) Reaction scheme of Huisgen cycloaddition used in click chemistry. The reaction is catalyzed by Cu(I) and requires alkyne and azide groups, one present on the target molecule and one on the detection tag. (C) Three examples of click-chemistry-ready sugar analogs used in the cell wall field: 6-alkynyl-fucose (Anderson et al., 2012), 6-deoxy-alkynyl glucose (McClosky et al., 2016) and 8-azido 8-deoxy Kdo (Dumont et al., 2016). (D) Proposed mechanism of incorporation of functionalizes, in this case fluorophore-tagged monolignols, into lignin according Tobimatsu et al. (2013).