Pectin-like heteroxylans in the early-diverging charophyte Klebsormidium fluitans

作者：Marie N. Rapin, John H. Bothwell, Stephen C. Fry · 发表于：Annals of Botany · 年份：2024 · DOI：10.1093/aob/mcae154 · 被引用次数：1 · 研究领域：Polysaccharides and Plant Cell Walls、Marine and coastal plant biology、Seaweed-derived Bioactive Compounds

BACKGROUND AND AIMS: The cell walls of charophytic algae both resemble and differ from those of land plants. Cell walls in early-diverging charophytes (e.g. Klebsormidiophyceae) are particularly distinctive in ways that might enable survival in environments that are incompatible with land-plant polymers. This study therefore investigates the structure of Klebsormidium polysaccharides. METHODS: The 'pectin' fraction (defined by extractability) of Klebsormidium fluitans, solubilized by various buffers from alcohol-insoluble residues, was digested with several treatments that (partly) hydrolyse land-plant cell-wall polysaccharides. Products were analysed by gel-permeation and thin-layer chromatography. KEY RESULTS: The Klebsormidium pectic fraction made up ~30-50 % of its alcohol-insoluble residue, was optimally solubilized at pH 3-4 at 100 °C, and contained residues of xylose ≈ galactose > rhamnose > arabinose, fucose, mannose and glucose. Uronic acids were undetectable, and the pectic fraction was more readily solubilized by formate than by oxalate, suggesting a lack of chelation. Some land-plant-targeting hydrolases degraded the Klebsormidium pectic fraction: digestion by α-l-arabinanase, endo-β-(1→4)-d-xylanase and α-d-galactosidase suggests the presence of β-(1→4)-xylan with terminal α-l-arabinose, α-d-galactose and (unexpectedly) rhamnose. 'Driselase' released oligosaccharides of xylose and rhamnose (~1:1), and graded acid hydrolysis of these oligosaccharides indicated a '...