Fig. 3. col requirement for emc upregulation and cell proliferation in the L3-L4 intervein primordium. Cell proliferation in wild-type (A) and col¹ (B) pupal wings, 18-20 hours APF, as visualised by the phosphorylation pattern of Histone H3 (H3P). (A) In wild type, a wave of cell proliferation occurs along veins in each intervein region at this stage, including the L3-L4 presumptive intervein (black frame) No such wave occurs in the medial region of a col¹ wing (B). (C,D) emc expression in third instar wing discs. Upregulation in the AP organiser of wild-type discs (C) is specifically lost in col¹ mutant discs (D). The small arrowhead and arrow indicate proveins L3 and L4, respectively.