UVR8 is localized in both the shoot and root, and is responsible for both shoot morphogenesis and root development. In the absence of UV‐B light, MYB73/MYB77 positively regulates the expression of auxin‐responsive genes and promotes hypocotyl elongation and lateral root development and growth. However, in the presence of UV‐B light, UV‐B induces the monomerization and nuclear accumulation of UVR8, which then interacts with MYB73/MYB77 in the nuclei. This interaction inhibits the DNA‐binding activity of MYB73/MYB77, thus repressing the expression of auxin‐responsive genes and auxin responses.