Figure 1.

Major classes of probes and key steps to image cell wall polysaccharides. A, Illustration of the steps required prior to microscopy (represented by the magnifying glasses) for different types of probes. Secondary antibodies (2° mAb) are commercially available and should be selected based on the final application (electron versus light microscopy) and the available equipment (e.g. fluorescence filters). Probes in colored boxes are exemplified in B to G. B and C, Sites of wall polysaccharide synthesis in Arabidopsis cotyledons expressing the yellow FP markers wave_22Y and wave_138Y, respectively (Geldner et al., 2009). FP signal and chloroplast intrinsic fluorescence are shown using Orange Hot and Cyan Hot look-up tables in Fiji (Schindelin et al., 2012). D to G, Mucilage architecture of an S4B-stained and mAb-labeled (CCRC-M36 and Alexa Fluor 488 2° mAb) Arabidopsis seed. D shows a segment of a whole seed (black) that has been brought into contact with water. The only clearly visible structures are columellae (C). S4B staining reveals cellulosic rays in E, and the antibody CCRC-M36 shows the deposition of rhamnogalacturonan in F. The comparison of the overlay G with D exemplifies the usefulness of dyes and labels. Bars = 25 µm (B–G).