The biosynthetic pathway for polysaccharides in Dendrobium officinale. The biosynthesis of polysaccharides contains sugar metabolism, UDP-saccharide metabolism, GDP-saccharide metabolism and polysaccharide formation. AR, aldose reductase; CSLA, cellulose synthase-like A; FRK, fructokinase; GAE, UDP-glucose A-4-epimerase; GER1, GDP-4-keto-6-deoxy-D-mannose-3,5-epimerase-4-reductase; GGP, glucose-1-phosphate guanylyltransferase; GGT, UDP-galacturonate decarboxylase; GMD, GDP-D-mannose-4,6-dehydratase; GMPP, mannose-1-phosphate guanylyl transferase; GPI, glucose-6-phosphate isomerase; GT, glycosyltransferases; HK, hexokinase; INV, invertase; KK, ketohexokinase; MAI, mannose isomerase; MPI, mannose-6-phosphate isomerase; PGM, phosphoglucomutase; PMM, phosphomannomutase; RHM, UDP-glucose 4, 6-dehydratase; RMD, GDP-4-dehydro-D-rhamnose reductase; SDH, sorbitol dehydrogenase; SPP, sucrose phosphate phosphatase; SPS, sucrose phosphate synthase; SuS, sucrose synthase; TSTA3, GDP-l-fucose synthase; UAE, UDP-glucuronate 4-epimerase; UAM, UDP-arabinopyranose mutase; UER1, 3,5-epimerase/4-reductase; UGDH, UDP-glucose dehydrogenase; UGE, UDP-glucuronate 4-epimerase; UGPase, UDP-glucose pyrophosphorylase; USP, UDP-sugar pyrophosphorylase; UXE, UDP-arabinose 4-epimerase; UXS1, UDP-glucuronate decarboxylase; XI, xylose isomerase; XK, xylulokinase.