A new approach in the field of plant gums is described which presents a new solution to the production of hydroxyproline(Hyp)-rich glycoproteins (HRGPs), repetitive proline-rich proteins (RPRPs) and arabino-galactan proteins (AGPs). The expression of synthetic genes designed from repetitive peptide sequences of such glycoproteins, including the peptide sequences of gum arabic glycoprotein (GAGP), is taught in host cells, including plant host cells.