Automated Glycan Assembly of Plant Oligosaccharides and Their Application in Cell‐Wall Biology

Abstract

The plant cell wall provides the richest available resource of fermentable carbohydrates and biobased materials. The main component of plant cell walls is cellulose, which is the most abundant biomolecule on earth. Apart from cellulose, which is constructed from relatively simple β‐1,4‐glucan chains, plant cell walls also contain structurally more complex heteropolysaccharides (hemicellulose and pectin), as well as lignin and cell‐wall proteins. A detailed understanding of the molecular structures, functions, and biosyntheses of cell‐wall components is required to further promote their industrial use. Plant cell‐wall research is, to a large degree, hampered by a lsack of available well‐defined oligosaccharide samples that represent the structural features of cell‐wall glycans. One technique to access these oligosaccharides is automated glycan assembly; a technique in which monosaccharide building blocks are, similarly to automated peptide and oligonucleotide chemistry, successively added to a linker‐functionalized resin in a fully automated manner. Herein, recent research into the automated glycan assembly of different classes of cell‐wall glycans used as molecular tools for cell‐wall biology is discussed. More than 60 synthetic oligosaccharides were prepared and printed as microarrays for screening monoclonal antibodies that recognize plant cell‐wall polysaccharides. The synthesized oligosaccharides have also been used to investigate glycosyltransferases and glycoside hydrolases, which are involved in synthesis and degradation of plant cell walls, as well as for the analysis of cell‐wall‐remodeling enzymes.

Cell wall‐derived mixed‐linked β‐1,3/1,4‐glucans trigger immune responses and disease resistance in plants

“…In addition, we decided to synthesize chemically the pure MLG structures to characterize the PTI activity of additional structures further. The analysis of Ca 2+ influxes triggered by these pure, synthetic structures indicated that MLG oligosaccharides with DP3 and DP4 were not active (Figure S6a), probably due to the presence of an aminoalkyl linker at their reducing end, which is required for the synthesis process (Figure S6c; Bartetzko and Pfrengle, 2019;Dallabernardina et al, 2017) and that would affect the tri-dimensional structures of these synthetic oligosaccharides and may interfere with their perception by PRRs. However, MLG oligosaccharides of higher DP (6 and 8) were active in triggering Ca 2+ influxes (Figure S6b; MLG44343 0 , MLG44434 0 , MLG43344 0 , MLG3434443 0 ).…”

A Glycan Array‐Based Assay for the Identification and Characterization of Plant Glycosyltransferases

“…We have recently developed a glycan array equipped with 88 synthetic plant oligosaccharides to determine the binding epitopes of cell wall glycan‐directed antibodies . These oligosaccharides represent fragments of natural hemicellulose, hydroxyproline‐rich glycoproteins, and pectic polysaccharides, and include arabinoxylan‐, type I and type II arabinogalactan‐, xyloglucan‐, and mixed‐linkage glucan‐ related structures . This array is being continuously expanded with newly synthesized oligosaccharides to increase the covered chemical space.…”

Progress and challenges in the synthesis of sequence controlled polysaccharides

“…The first solution phase synthesis of a nonasaccharide repeating unit was realized using a convergent approach [ 101 ]. The process was later simplified using AGA and several XG oligosaccharides were prepared [ 102 ]. Representative examples are 19 and 20 ( Scheme 3 ) [ 103 ], as well as the galactose-containing compounds 21 and 22 [ 104 ].…”