Auxin response to compounds. A to D, Images of GUS-stained DR5::GUS leaves with indicated treatment viewed with dark-field optics. A, Series of a developing wild-type leaf shows progressively diminishing DR5::GUS reporter expression in veins. B, Treatment with PATI-1, PATI-4, and HYVP-1 dramatically broadens the pattern of DR5::GUS expression. lf, Leaf. C, OVP-1 causes reduced DR5::GUS expression consistent with reduced vein number. D, OVP-2-treated leaves exhibit sustained DR5::GUS vascular expression throughout the leaf. Strong and weak GUS is indicated by blue and pink colors, respectively. E, Auxin response in compound-treated roots. Images are of 4-d-old GUS-stained DR5::GUS seedling roots treated with compound in absence (left) or presence (right) of auxin (IAA). PATI-1 inhibits auxin response in contrast to the remaining CAVPs, which have no effect. Concentrations: 1 µm, PATI-3; 10 µm, NPA, PEO-IAA, PATI-1, -2, and -4; 25 µm, HYVPs; 1 µm IAA. Bars, 250 µm (A–D) and 500 µm (E).