The pattern of xylan acetylation suggests xylan may interact with cellulose microfibrils as a two-fold helical screw in the secondary plant cell wall of Arabidopsis thaliana.
Gomes, Thiago CF
Grantham, Nicholas J
Bolam, David N
Skaf, Munir S
The Plant Journal
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Busse-Wicher, M. N., Gomes, T. C., Tryfona, T., Nikolovski, N., Stott, K. M., Grantham, N. J., Bolam, D. N., et al. (2014). The pattern of xylan acetylation suggests xylan may interact with cellulose microfibrils as a two-fold helical screw in the secondary plant cell wall of Arabidopsis thaliana.. The Plant Journal https://doi.org/10.1111/tpj.12575
The interaction between xylan and cellulose microfibrils is important for secondary cell wall properties in vascular plants. However, the molecular arrangement of xylan in the cell wall and the nature of the molecular bonding between the polysaccharides are unknown. In dicots, the xylan backbone of β-(1,4)-linked xylosyl residues is decorated by occasional glucuronic acid and approximately one half of the xylosyl residues are O-acetylated at C-2 or C-3. We recently proposed that the even periodic spacing of GlcA residues in the major domain of dicot xylan might allow the xylan backbone to fold as a 2-fold helical screw to facilitate alignment along, and stable interaction with, cellulose fibrils (Bromley et al. 2013). However, such an interaction might be adversely impacted by random acetylation of the xylan backbone. Here, we investigated the arrangement of acetyl residues in Arabidopsis xylan using mass spectrometry and NMR. Alternate xylosyl residues along the backbone are acetylated. Using molecular dynamics simulation, we found that a 2- fold helical screw conformation of xylan is stable in interactions with both hydrophilic and hydrophobic cellulose faces. Tight docking of xylan on the hydrophilic faces is feasible only for xylan decorated on alternate residues and folded as a 2-fold helical screw. The findings suggest an explanation for the importance of acetylation for xylan–cellulose interactions, and also have implications for our understanding of cell wall molecular architecture and properties, and biological degradation by pathogens and fungi. They will also impact strategies to improve lignocellulose processing for biorefining and bioenergy.
Xylan, acetylation, plant cell wall molecular architecture, cellulose interaction, Arabidopsis thaliana
The work conducted by TT and NN was supported by a grant from the BBSRC: BB/G016240/1 BBSRC Sustainable Energy Centre Cell Wall Sugars Programme (BSBEC) to PD and DNB. The work of PD was supported by the European Community’s Seventh Framework Programme SUNLIBB (FP7/2007-2013) under the grant agreement #251132. The NMR facility infrastructure was supported by the BBSRC and the Wellcome Trust. TCFG thanks CNPq (Brazil) for a graduate fellowship (grant # 140978/2009-7). MSS thanks CEPROBIO (grant # 490022/2009- 0) and FAPESP for funding (grant #2013/08293-7).
External DOI: https://doi.org/10.1111/tpj.12575
This record's URL: https://www.repository.cam.ac.uk/handle/1810/245387