Characterization of the linkage between xyloglucan and pectin in Arabidopsis thaliana culture cell walls
Abstract
Xyloglucan, a major cross-linking glycan in the primary cell wall of most eudicots, has been considered to be independent of the pectic network. However, several groups have found strong evidence for a covalent attachment to pectin in walls of cell cultures. There has only been speculation on the nature of the linkage between xyloglucan and pectin. Isolation of a crosslinking fragment between pectin and xyloglucan has been elusive. The Mort lab has been working on this for thirty years with limited success. We isolated the pectin-associated xyloglucan from Arabidopsis thaliana suspension cell cultures using anion exchange chromatography. Endo-arabinanase was then used to release xyloglucan from the pectin. An arabinose residue was found in dissociated xyloglucan and found to be at the reducing end instead of sidechains of the released xyloglucan. A similar arabinose-containing linkage was also found in the pectin-unbound free xyloglucan, possibly existing as an intermediate of xyloglucan-pectin conjugation. Part of the pectin-associated xyloglucan was not covalently linked to the pectin. Such a tight non-covalent interaction survived strong alkali, heat, and concentrated salt elution. Debranching rhamnogalacturonan-I with exo-arabinosidase or heating at 80 degrees C could release much of the non-covalently bound xyloglucan. Much remains to be learned about the interactions between pectins and xyloglucans and their roles in cell wall function.
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- OSU Dissertations [11222]