Arabinogalactan-proteins (AGPs) are ubiquitous components of cell walls throughout the plant kingdom and are extensively post translationally modified by conversion of proline to hydroxyproline (Hyp) and by addition of arabinogalactan polysaccharides (AG) to Hyp residues. | A small multigene hydroxyproline-Ogalactosyltransferase family functions in arabinogalactan-protein glycosylation growth and development in Arabidopsis