Xyloglucan in the primary cell wall: assessment by FESEM, selective enzyme digestions and nanogold affinity tags

Citations Over TimeTop 10% of 2017 papers

Abstract

Xyloglucan has been hypothesized to bind extensively to cellulose microfibril surfaces and to tether microfibrils into a load-bearing network, thereby playing a central role in wall mechanics and growth, but this view is challenged by newer results. Here we combined high-resolution imaging by field emission scanning electron microscopy (FESEM) with nanogold affinity tags and selective endoglucanase treatments to assess the spatial location and conformation of xyloglucan in onion cell walls. FESEM imaging of xyloglucanase-digested cell walls revealed an altered microfibril organization but did not yield clear evidence of xyloglucan conformations. Backscattered electron detection provided excellent detection of nanogold affinity tags in the context of wall fibrillar organization. Labelling with xyloglucan-specific CBM76 conjugated with nanogold showed that xyloglucans were associated with fibril surfaces in both extended and coiled conformations, but tethered configurations were not observed. Labelling with nanogold-conjugated CBM3, which binds the hydrophobic surface of crystalline cellulose, was infrequent until the wall was predigested with xyloglucanase, whereupon microfibril labelling was extensive. When tamarind xyloglucan was allowed to bind to xyloglucan-depleted onion walls, CBM76 labelling gave positive evidence for xyloglucans in both extended and coiled conformations, yet xyloglucan chains were not directly visible by FESEM. These results indicate that an appreciable, but still small, surface of cellulose microfibrils in the onion wall is tightly bound with extended xyloglucan chains and that some of the xyloglucan has a coiled conformation.

Related Papers

• → Xyloglucan and its Interactions with Other Components of the Growing Cell Wall(2015)417 cited
• → Characterization of the Cell-Wall Polysaccharides of Arabidopsis thaliana Leaves(1995)387 cited
• → Composition and desiccation‐induced alterations of the cell wall in the resurrection plant Craterostigma wilmsii(2004)105 cited
• → Cell Wall Characteristics and Structure of Hydrated and Dry leaves of the Resurrection Plant Craterostigma wilmsii, a Microscopical Study(1999)80 cited
• → Action of Xyloglucan Hydrolase within the Native Cell Wall Architecture and Its Effect on Cell Wall Extensibility in Azuki Bean Epicotyls(2002)52 cited