Xyloglucan undergoes interpolymeric transglycosylation during binding to the plant cell wall in vivo: evidence from 13C/3H dual labelling and isopycnic centrifugation in caesium trifluoroacetate.

摘要: Xyloglucan from the walls of Rosa cells that had been cultured on [12C]- or [13C]-glucose formed bands in caesium trifluoroacetate with mean buoyant densities 1.575 1.616 g/ml respectively. Incubation a mixture [13C,3H]xyloglucan and [12C,1H]xyloglucan presence xyloglucan endotransglycosylase (XET) activity caused density radioactive material to decrease, indicating interpolymeric transglycosylation could be detected vitro. We used two 13C/3H-dual-labelling protocols look for vivo. In protocol A, [13C]glucose-grown were transferred into [12C]glucose medium 6 h after approximately 2 pulse l-[1-3H]arabinose (which radiolabels xylose residues xyloglucan). The wall-bound [3H]xyloglucan decreased during following 7 days culture. This indicates that, wall-binding newly synthesized [12C,1H]xyloglucan, it became covalently attached previously [13C, 3H]xyloglucan. B, [12C]glycerol- [12C]glucose-grown [13C]glucose medium, 20 60 min before [3H]arabinose. earliest showed 12C/13C ratio 1:1. (or, implausibly, before) wall-binding, 3H]xyloglucan [12C]xyloglucan. During culture, increased, showing later-synthesized [13C,1H]xyloglucan can [12C,13C,3H]xyloglucan. only known mechanism by which segments xyloglucans become each other cell wall is catalysed XET. conclude XET-catalysed accompanies, probably causes, integration secreted cell-wall architecture.