title: The ability of land plants to synthesize glucuronoxylans predates the evolution of tracheophytes.
abstract: Glucuronoxylans with a backbone of 1,4-linked β-D-xylosyl residues are ubiquitous in the secondary walls of gymnosperms and angiosperms. Xylans have been reported to be present in hornwort cell walls, but their structures have not been determined. In contrast, the presence of xylans in the cell walls of mosses and liverworts remains a subject of debate. Here we present data that unequivocally establishes that the cell walls of leafy tissue and axillary hair cells of the moss Physcomitrella patens contain a glucuronoxylan that is structurally similar to glucuronoxylans in the secondary cell walls of vascular plants. Some of the 1,4-linked β-D-xylopyranosyl residues in the backbone of this glucuronoxylan bear an α-D-glucosyluronic acid (GlcpA) sidechain at O-2. In contrast, the lycopodiophyte Selaginella kraussiana synthesizes a glucuronoxylan substituted with 4-O-Me-α-D-GlcpA sidechains, as do many hardwood species. The monilophyte Equisetum hyemale produces a glucuronoxylan with both 4-O-Me-α-D-GlcpA and α-D-GlcpA sidechains, as does Arabidopsis. The seedless plant glucuronoxylans contain no discernible amounts of the reducing-end sequence that is characteristic of gymnosperm and eudicot xylans. Phylogenetic studies showed that the P. patens genome contains genes with high sequence similarity to Arabidopsis CAZy family GT8, GT43 and GT47 glycosyltransferases that are likely involved in xylan synthesis. We conclude that mosses synthesize glucuronoxylan that is structurally similar to the glucuronoxylans present in the secondary cell walls of lycopodiophytes, monilophytes, and many seed-bearing plants, and that several of the glycosyltransferases required for glucuronoxylan synthesis evolved before the evolution of tracheophytes.
authors: Complex Carbohydrate Research Center and US Department of Energy Bioenergy Science Center, Athens, GA 30602, USA.
authors: Ameya R
authors: AR
authors: Kulkarni
authors: Maria J
authors: MJ
authors: Peña
authors: Utku
authors: U
authors: Avci
authors: Koushik
authors: K
authors: Mazumder
authors: Breeanna R
authors: BR
authors: Urbanowicz
authors: Sivakumar
authors: S
authors: Pattathil
authors: Yanbin
authors: Y
authors: Yin
authors: Malcolm A
authors: MA
authors: O'Neill
authors: Alison W
authors: AW
authors: Roberts
authors: Michael G
authors: MG
authors: Hahn
authors: Ying
authors: Y
authors: Xu
authors: Alan G
authors: AG
authors: Darvill
authors: William S
authors: WS
authors: York
mesh_terms: D019068:Bryopsida / Q000166:cytology / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D002236:Carbohydrate Conformation; D002473:Cell Wall / Q000378:metabolism; D019143:Evolution, Molecular; D029624:Ferns / Q000235:genetics* / Q000378:metabolism; D018745:Genome, Plant; D005965:Glucuronates / Q000737:chemistry; D016695:Glycosyltransferases / Q000235:genetics; D009844:Oligosaccharides / Q000737:chemistry; D010802:Phylogeny; D018515:Plant Leaves / Q000166:cytology / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics; D058526:Plant Vascular Bundle / Q000235:genetics; D010944:Plants / Q000033:anatomy & histology / Q000235:genetics / Q000378:metabolism; D014990:Xylans / Q000096:biosynthesis*
chemical_list: D005965:Glucuronates; D009844:Oligosaccharides; D010940:Plant Proteins; D014990:Xylans; C570991:xylooligosaccharide; C038910:glucuronoxylan; D016695:Glycosyltransferases