Fig. 4. Expression pattern of the different so10 enhancers. (A) Schematic drawing of the enhancer with the different EY and TOY binding sites indicated by five boxes. The different mutated so10 enhancers used are represented using crossed boxes. All panels in a column refer to the same so10 enhancer. (B-E) Early third instar eye discs and (F-I) late third instar eye discs. During larval stages the lacZ transgene was detected by staining for ß-galactosidase. For all eye discs, posterior is left and dorsal is towards the top. During early third instar larval stage the expression is lost in the central part of the eye disc when the EY binding sites are mutated (D), in contrast to mutations of the TOY binding sites which show no obvious defects at this stage (C). At late third instar stage mutations of the TOY binding sites restrict expression to the posterior edge of the eye disc (G) whereas mutations of the EY binding sites do not alter the expression pattern from second to third instar larvae (D,H). Expression is completely abolished in the eye primordium and in the eye disc when all five binding sites are mutated (E,I).