Pectin-like heteroxylans in the early-diverging charophyte <i>Klebsormidium fluitans</i>

Klebsormidium pectic fraction possesses many land-plant-like linkages but is unusual in lacking uronic acid residues and in containing rhamnoxylan and galactoxylan domains. Uronic acids allow land-plant and late-diverging charophyte pectins to form Ca2+-bridges, facilitating cell-wall polymer association; their absence from Klebsormidium suggests that neutral heteroxylans rely on alternative cross-linking mechanisms. This lack of dependence on Ca2+-bridges might confer on Klebsormidium the ability to grow in the acidic, metal-rich environments that it tolerates.