Flavonol 7-O-rhamnosyltransferase that catalyzes the transfer of rhamnose from UDP-rhamnose to the 7-OH position of 3-O-glycosylated flavonols, such as kaempferol 3-O-rhamnoside, kaempferol 3-O-glucoside, quercetin 3-O-glucoside, quercetin 3-O-galactoside, quercetin 3-O-rhamnoside and isorhamnetin 3-O-glucoside (PubMed:17314094, PubMed:23549747, PubMed:24251900, PubMed:30893500). Is able to glycosylate the flavonols quercetin and kaempferol to yield quercetin 7-O-rhamnoside and kaempferol 7-O-rhamnoside (PubMed:17314094, PubMed:26513760, PubMed:30893500). Shows a strict specificity for UDP-rhamnose as sugar donor (PubMed:17314094, PubMed:30893500). Does not act on 3-O-glycosylated anthocyanins (PubMed:17314094). The accumulation of kaempferol 3-O-rhamnoside-7-O-rhamnoside inhibits basipetal auxin transport, which influences auxin distribution and plant organ development (PubMed:24251900, PubMed:26742840). quercitrin + UDP-beta-L-rhamnose = H(+) + quercetin 3,7-bis-O-alpha-L-rhamnoside + UDP quercetin 3-O-beta-D-glucoside + UDP-beta-L-rhamnose = H(+) + quercetin 3-O-beta-D-glucoside-7-O-alpha-L-rhamnoside + UDP Flavonoid metabolism. Highly expressed in floral buds (PubMed:17314094). Expressed in stems, leaves and flowers (PubMed:17314094). Expressed at low levels in roots and siliques (PubMed:17314094). Expressed on the adaxial side of cotyledons and emerging leaves, in trichomes, root columella cells, and the late elongation/early differentiation zone of roots (PubMed:26742840). No visible phenotype under normal growth conditions, but mutant plants do not accumulate 7-O-rhamnosylated flavonols (PubMed:17314094, PubMed:24251900, PubMed:26742840). Increased concentrations of auxin precursors and auxin metabolites (PubMed:26742840). Belongs to the UDP-glycosyltransferase family.