Requirement of borate cross-linking of cell wall rhamnogalacturonan II for Arabidopsis growth

Turgor-driven plant cell growth depends on watt structure. Two allelic L-fucose-deficient Arabidopsis thaliana mutants (mur1-1 and 1-2) are dwarfed and their rosette leaves do not grow normally. mur1 leaf cell watts contain normal amounts of the cell watt pectic polysaccharide rhamnogalacturonan II (RG-II), but only half exists as a borate cross-linked dimer. The altered structure of mur1 RG-II reduces the rate of formation and stability of this cross-link. Exogenous aqueous borate rescues the defect. The reduced cross-linking of RG-II in dwarf mur1 plants indicates that plant growth depends on watt pectic polysaccharide organization.