title: O-acetylation of glucuronoxylan in Arabidopsis thaliana wild type and its change in xylan biosynthesis mutants.
abstract: O-Acetylglucuronoxylans (AcGX) in Arabidopsis thaliana carry acetyl residues on the 2-O and/or 3-O positions of the xylopyranosyl (Xylp) units, but the distribution of different O-acetylated Xylp units is partly unclear. We studied a possible correlation of xylan acetylation and the activities of different glycosyltransferases involved in xylan biosynthesis by analyzing the distribution of O-acetyl substituents on AcGX from Arabidopsis wild-type and mutants irx7, irx9-1, irx10, irx14 and gux1gux2. The relative contents of the Xylp structural units were determined with quantitative two-dimensional heteronuclear single quantum coherence nuclear magnetic resonance spectroscopy. In the wild type, the degree of acetylation (DA) was 60%. Mono- and diacetylated Xylp units constituted 44 and 6% of the AcGX backbone, respectively; while (4-O-methyl)-glucopyranosyluronic acid (1 → 2)-linked Xylp units, most of which also carry 3-O-acetylation, represented 13%. The DA was decreased in irx7, irx9-1 and irx14 due to the decrease in monoacetylation (2-O and 3-O), indicating a relationship between acetylation and other AcGX biosynthetic processes. The possible interactions that could lead to such changes have been discussed. No change in DA was observed in irx10 and gux1gux2, but monoacetylation was nonetheless elevated in gux1gux2. This indicates that acetylation occurs after addition of GlcpA to the xylan backbone. Mass fragmentation analysis suggests that the prevalent acetylation pattern is the acetyl group added on every other Xylp unit.
authors.affiliation: Department of Food and Environmental Sciences, Faculty of Agriculture and Forestry, University of Helsinki, PO Box 27, 00014, Finland.
authors.forename: Sun-Li
authors.initials: SL
authors.lastname: Chong
authors.forename: Liisa
authors.initials: L
authors.lastname: Virkki
authors.forename: Hannu
authors.initials: H
authors.lastname: Maaheimo
authors.forename: Minna
authors.initials: M
authors.lastname: Juvonen
authors.forename: Marta
authors.initials: M
authors.lastname: Derba-Maceluch
authors.forename: Sanna
authors.initials: S
authors.lastname: Koutaniemi
authors.forename: Melissa
authors.initials: M
authors.lastname: Roach
authors.forename: Björn
authors.initials: B
authors.lastname: Sundberg
authors.forename: Päivi
authors.initials: P
authors.lastname: Tuomainen
authors.forename: Ewa J
authors.initials: EJ
authors.lastname: Mellerowicz
authors.forename: Maija
authors.initials: M
authors.lastname: Tenkanen
mesh_terms: D000107:Acetylation; D017360:Arabidopsis / Q000201:enzymology / Q000235:genetics; D018506:Gene Expression Regulation, Plant; D016695:Glycosyltransferases / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D014990:Xylans / Q000096:biosynthesis* / Q000737:chemistry / Q000378:metabolism
chemical_list: D014990:Xylans; C038910:glucuronoxylan; D016695:Glycosyltransferases
keywords: Arabidopsis; GlucUronic acid substitution of xylan (GUX); irregular xylem; secondary wall; xylan acetylation