PTOV1 antagonizes Notch activity in the Drosophila wing. (A) Expression of hPTOV1 in engrailed-Gal4UAS-GFP; UAS-HA-hPTOV1 wing imaginal discs. To confirm the activity of the transgene, the ectopic expression of hPTOV1 from the UAS-HA-hPTOV1 was examined. The engrailed-Gal4 line, which drives UAS-transgene expression only in the posterior compartment of the wing disc, allows to compare the levels of expression in anterior versus posterior compartments in the same tissue (imaginal disc). The expression of the transgene was observed by (1) co-activation of a UAS-GFP, (2) immuno detection of HA and (3) antibodies to PTOV1. Absence of staining in the anterior (left) half of the disc contrasts with positive staining in the posterior (right) half, demonstrating the ectopic expression of PTOV1 driven by engrailed-Gal4. (B) Overxpression of hPTOV1 exacerbates the effects of loss-of-function (LOF) of Notch. Notch LOF allele N55e11causes a notch at the wing edge (arrowhead, left and middle panels) that is exacerbated by expression of hPTOV1 (arrowheads, right panel). (C) Expression of hPTOV1 suppresses the effects of Notch gain-of-function (GOF). The GOF Notch allele NAx-M1causes defects in the L5 vein (arrowhead, left and middle panels), suppressed by expression of hPTOV1 (arrowhead, right panel). A wild type (wt) wing is shown as control. (D) Histogram showing the quantification of the wing areas for each genotype (n > 30) (*** p < 0.0005).