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Plant Cell. 2018 Jun;30(6):1293-1308. doi: 10.1105/tpc.18.00082. Epub 2018 Apr 19.

Functional Characterization of a Glycosyltransferase from the Moss Physcomitrella patens Involved in the Biosynthesis of a Novel Cell Wall Arabinoglucan.

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Department of Biological Sciences, University of Rhode Island, Kingston, Rhode Island 02881
ARC Centre of Excellence in Plant Cell Walls, School of Agriculture, Food, and Wine, University of Adelaide, Urrbrae, South Australia 5064, Australia.
Division of Glycoscience, Department of Chemistry, School of Engineering Sciences in Chemistry, Biotechnology, and Health, Royal Institute of Technology (KTH), Stockholm SE-10691, Sweden.
Department of Biological Sciences, University of Rhode Island, Kingston, Rhode Island 02881.
ARC Centre of Excellence in Plant Cell Walls, Plant Cell Biology Research Centre, School of BioSciences, The University of Melbourne, Victoria 3010, Australia.
Biology Department, Rhode Island College, Providence, Rhode Island 02908.


Mixed-linkage (1,3;1,4)-β-glucan (MLG), an abundant cell wall polysaccharide in the Poaceae, has been detected in ascomycetes, algae, and seedless vascular plants, but not in eudicots. Although MLG has not been reported in bryophytes, a predicted glycosyltransferase from the moss Physcomitrella patens (Pp3c12_24670) is similar to a bona fide ascomycete MLG synthase. We tested whether Pp3c12_24670 encodes an MLG synthase by expressing it in wild tobacco (Nicotiana benthamiana) and testing for release of diagnostic oligosaccharides from the cell walls by either lichenase or (1,4)-β-glucan endohydrolase. Lichenase, an MLG-specific endohydrolase, showed no activity against cell walls from transformed N. benthamiana, but (1,4)-β-glucan endohydrolase released oligosaccharides that were distinct from oligosaccharides released from MLG by this enzyme. Further analysis revealed that these oligosaccharides were derived from a novel unbranched, unsubstituted arabinoglucan (AGlc) polysaccharide. We identified sequences similar to the P. patens AGlc synthase from algae, bryophytes, lycophytes, and monilophytes, raising the possibility that other early divergent plants synthesize AGlc. Similarity of P. patens AGlc synthase to MLG synthases from ascomycetes, but not those from Poaceae, suggests that AGlc and MLG have a common evolutionary history that includes loss in seed plants, followed by a more recent independent origin of MLG within the monocots.

[Available on 2019-06-01]

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