Structural diversity of xylans in the cell walls of monocots
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Xylans in the cell walls of monocots are structurally diverse. Arabinofuranose-containing glucuronoxylans are characteristic of commelinids. However, other structural features are not correlated with the major transitions in monocot evolution.
Most studies of xylan structure in monocot cell walls have emphasized members of the Poaceae (grasses). Thus, there is a paucity of information regarding xylan structure in other commelinid and in non-commelinid monocot walls. Here, we describe the major structural features of the xylans produced by plants selected from ten of the twelve monocot orders. Glucuronoxylans comparable to eudicot secondary wall glucuronoxylans are abundant in non-commelinid walls. However, the α-d-glucuronic acid/4-O-methyl-α-d-glucuronic acid is often substituted at O-2 by an α-l-arabinopyranose residue in Alismatales and Asparagales glucuronoxylans. Glucuronoarabinoxylans were the only xylans detected in the cell walls of five different members of the Poaceae family (grasses). By contrast, both glucuronoxylan and glucuronoarabinoxylan are formed by the Zingiberales and Commelinales (commelinids). At least one species of each monocot order, including the Poales, forms xylan with the reducing end sequence -4)-β-d-Xylp-(1,3)-α-l-Rhap-(1,2)-α-d-GalpA-(1,4)-d-Xyl first identified in eudicot and gymnosperm glucuronoxylans. This sequence was not discernible in the arabinopyranose-containing glucuronoxylans of the Alismatales and Asparagales or the glucuronoarabinoxylans of the Poaceae. Rather, our data provide additional evidence that in Poaceae glucuronoarabinoxylan, the reducing end xylose residue is often substituted at O-2 with 4-O-methyl glucuronic acid or at O-3 with arabinofuranose. The variations in xylan structure and their implications for the evolution and biosynthesis of monocot cell walls are discussed.
KeywordsMonocot Cell wall Glucuronoarabinoxylan Glucuronoxylan
4-O-Methyl glucuronic acid
- 13C NMR
Carbon nuclear magnetic resonance spectroscopy
- 1H NMR
Proton nuclear magnetic resonance spectroscopy
MS matrix-assisted laser desorption time-of-flight mass spectrometry
This research was funded by the BioEnergy Science Center (BESC). BESC is a U.S. Department of Energy Bioenergy Research Center supported by the Office of Biological and Environmental Research in the DOE Office of Science. We also acknowledge the U.S. Department of Energy-funded Center for Plant and Microbial Complex Carbohydrates (Grant DE-FG02-93ER20097) for equipment support.
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Conflict of interest
The authors declare that they have no conflict of interest
- Chase M, Fay MF, Devey DS, Maurin O, Rønsted N, Davies TJ, Pillon Y, Petersen G, Seberg O, Tamura M (2006) Multigene analyses of monocot relationships: a summary. Aliso 22:63–75Google Scholar
- Harris P (2006) Primary and secondary plant cell walls: a comparative overview. N Zeal J For Sci 36:36–53Google Scholar
- Landolt E (1986) Biosystematic investigation in the family of duckweeds (“Lemnaceae”). The family of “Lemnaceae”: a monographic study, vol 2. Veröffentlichungen des Geobotanischen Institutes der ETH, ZürichGoogle Scholar
- Urbanowicz BR, Peña MJ, Ratnaparkhe S, Avci U, Backe J, Steet HF, Foston M, Li H, O’Neill MA, Ragauskas AJ, Darvill AG, Wyman C, Gilbert HJ, York WS (2012) 4-O-methylation of glucuronic acid in Arabidopsis glucuronoxylan is catalyzed by a domain of unknown function family 579 protein. Proc Nat Acad Sci USA 109:14253–14258CrossRefPubMedPubMedCentralGoogle Scholar