Fig. 2. soAE is a direct target of so. soAE (sine oculis autoregulatory element) corresponds to fragment number 21. Arrows indicate the ocellar region. (A-C) soAE harbours three putative transcription-factor-binding sites, which have been mutated. (A) Mutating the core of the HD recognition sequence (mutHD) or (B) mutating the GATA sequence (mutGATA) abolishes expression of the lacZ reporter in the ocellar region. (C) so10-mutPAX in which the putative Pax6-binding site is mutated, mediates expression indistinguishable from wt/so10-soAE-mediated expression. (D-F) Oligomerization of soAE boosts its expression. By contrast to soAE alone, which only mediates expression in the posterior margin of the eye disc (D), 4xsoAE drives expression posterior of the MF, within the MF and in some cells in front of the MF, but not in the ocellar region (E). This expression resembles wt so-expression despite the ocellar region. (F) 10xsoAE does not further amplify expression intensity but results in a more blotchy type of expression pattern. (G) Sequences of soAE and the mutated versions of it. Sequences TAA and GAT of soAE are important for the ocellus-specific expression of so10-soAE-lacZ. (F) Radiolabelled probes of mutHD and mutGATA are not shifted by SO in EMSA. By contrast, mutPAX is bound by SO and therefore shifted in EMSA.