Fig. 1. Knockdown of PP4 elevates Smo accumulation in wing discs. (A-A'') A wing disc expressing GFP by ap-Gal4 was stained with anti-SmoN, β-gal (for ptc-lacZ expression). GFP indicates the ap-Gal4 expression domain in wing disc. (B-B'') UAS-PP4RNAi was expressed by ap-Gal4 and immunostained for Smo and ptc-lacZ expression. Arrowhead in B indicates the accumulation of Smo and arrowhead in B' indicates the anterior expansion of ptc-lacZ. (C-C'') As expressing UAS-MtsRNAi by the ap-Gal4 caused cell lethality, the weak act>CD2>Gal4 was used and larvae were grown at 20°C to reduce the Gal4 levels, thus limiting the strength of Mts RNAi. (D,D') A wing disc expressing UAS-HA-PP4 by ap-Gal4 was immunostained for Smo and HA. (E) A wing disc co-expressing UAS-PP4RNAi and UAS-HA-PP4 was immunostained with anti-SmoN antibody. Arrowhead indicates that HA-PP4 reduces the levels of Smo accumulation that are caused by PP4 RNAi. (F,F') A wing disc expressing UAS-Mts by ap-Gal4 was immunostained with anti-SmoN antibody. (G) A wing disc co-expressing UAS-Mts with UAS-PP4RNAi by ap-Gal4 was stained with anti-SmoN antibody. All wing discs shown in this study were oriented with anterior towards the left and ventral towards the top.