Figure 1.

Fluorescent probes for cell wall polysaccharide imaging. The structures of the cellulose-binding dye Pontamine Fast Scarlet 4B (S4B) (A) and the xyloglucan-binding dye Solophenyl Flavine 7GFE (B). (C) A generalized version of the copper-catalyzed Huisgen [2 + 3] cycloaddition reaction. This reaction is useful for coupling molecules containing terminal alkynyl or azido groups, such as per-acetylated fucose alkyne (FucAl) (D) and Alexa-488 azide (E). Sugar analogs such as FucAl can be metabolically incorporated into glycans via the action of sugar salvage pathways and cognate glycosyltransferases, producing modified polysaccharides that can be labeled with azido-containing fluorophores by the click reaction. This strategy was used in Anderson et al. (2012) to metabolically label pectins by incorporating FucAl into the root tissue of Arabidopsis followed by copper-catalyzed labeling as shown in (F). A representative image of root epidermal cells in the late elongation zone after labeling is shown in the right panel.