E(spl) prevents precocious 5’-ato activation.

Mitotic clones were generated using the FLP-FRT recombination system [57]. WT and heterozygous tissue is marked by GFP (magenta), mutant clones are marked by the absence of GFP. (A-D) As compared to WT eye-antennal discs (A), E(spl) mutant tissue features persistent, unpatterned Ato (cyan) expression. (E-H) ato-3’–lacZ enhancer reports in a dorsoventral band that initiates within the MF (E). Loss of E(spl) fails to elicit any notable effect on ato-3’ expression (cyan). (I-L) 5-‘ato-lacZ report mimics IG and R8 patterning of Ato, with the exception that reporter is observed in R8s throughout the posterior of the tissue (I). E(spl) mutants feature reporter signal (cyan) that is stronger than in WT and is observed anterior of WT or heterozygous tissues. Yellow arrowhead denotes position of MF; scale bars = 20μm. Genotypes: (A) w¹¹¹⁸, (B-D) FRT82B Df(3R)E(spl)^b32.2 P{gro⁺}/FRT82B ubiGFP eyFLP, (E) P{w^+mC ato3’F:5.8}/+, (F-H) P{w^+mC ato3’F:5.8/+; FRT82B Df(3R)E(spl)^b32.2 P{gro⁺}/FRT82B ubiGFP eyFLP, (I) P{w^+mC ato5’F:9.3}/+, (J-L) P{w^+mC ato5’F:9.3}/+, FRT82B Df(3R)E(spl)^b32.2 P{gro⁺}/FRT82B ubiGFP eyFLP.