FIG. 9.

Deletion of smvs containing Dorsal, Twi, and Sna E-box binding sites results in loss of mesectodermal transcription. Mutations in the 2.8-kb sim early regulatory region were created, cloned into a P[lacZ] vector, and tested for mesectodermal lacZ transcription after introduction into germline DNA. The constructs tested are shown beneath a schematic of the 2.8-kb regulatory region with numbered smvs. Each construct listed with the smv deleted (D) is indicated by an “X” through the relevant number. P[2.8simΔSΔ16] deletes Sna sites S4, S5 (S), and smv 16. P[simB] is a construct with sim gene fragment B cloned into an enhancer tester P[lacZ] vector. P[simB2x16] contains fragment B and 2 copies of the SE6 and SE7 Sna binding sites. Presence of strong blastoderm mesectodermal (MEC) lacZ transcription is indicated to the right by (+), weak expression by (+/–), and the absence of expression by (–). The binding sites deleted in each construct are listed to the right. The bracketed sites listed for P[simB] and P[simB2x16] indicate binding sites that are included in the construct. Representative embryos for each construct are shown at the bottom.