Flavonol-specific transcription activator involved in the regulation of several genes of flavonoid biosynthesis. Activates the expression of CHS, CHI, F3H and FLS1. Controls flavonol biosynthesis primarily in cotyledons and leaves (PubMed:17419845, PubMed:20731781). Confers tolerance to UV-B (PubMed:19895401). Expressed in seedlings, cotyledons and young leaves. In seedlings, predominantly expressed in cotyledons. Restricted to the cotyledons and primary leaves. Triggered by HY5 in response to light and UV-B. Reduced flavonols levels in leaves. The double mutants myb11 myb111 and myb12 myb111 and triple mutant myb11 myb12 myb111 accumulate less flavonols in roots, leaves, stems, inflorescence, and siliques (PubMed:20731781). The triple mutant myb11 myb12 myb111 is impaired in flavonols biosynthesis and exhibits a reduced UV-B tolerance (PubMed:17419845, PubMed:19895401). Promotes flavonoid biosynthesis in a light-dependent manner when expressed in tobacco (Nicotiana tabacum) through up-regulation of the biosynthetic genes.