6-02: Distribution of cell wall glycans in switchgrass (Panicum virgatum)

Plant cells are surrounded by a dynamic extracellular matrix called the cell wall that undergoes modifications in composition and configuration depending on the developmental stage and external factors such as environmental stress or interactions with pathogenic and symbiotic microbes.  In order to better understand the cell wall architecture, it is necessary to visualize the components of the cell wall in vitro and in situ.  Cell wall-directed specific monoclonal antibodies are useful tools to examine the distribution of wall polymers in plant cell walls at the whole plant, tissue, cell, and sub-cellular levels. 

The monocot, switchgrass (Panicum virgatum), is currently of interest as a potential source of biomass for biofuel production.  Here we show that the antibody toolkit can be used to localize wall polysaccharide epitopes in switchgrass leaf blade, leaf sheath, and stem.  The epitope localization patterns observed switchgrass are similarly complex to those observed in dicots, such as Arabidopsis, although the patterns are different for several antibodies.  For example, xylan-directed antibodies label a much broader diversity of cell types in switchgrass than has been observed in Arabidopsis.  In contrast, homogalacturonan-directed antibodies label only cell corners and cell-cell interfaces in switchgrass, in contrast to Arabidopsis where these antibodies label whole cell walls.  These data are also supported by glycome profiling and glycosyl compositional analysis. A detailed understanding of polysaccharide localization patterns has the potential to identify potential targets for either modification or degradation that will lead to more efficient deconstruction of biomass into fermentable monosaccharides for biofuel production.