Fig. 2.

Widespread expression of active TeTxLC (inactive, Mz1369/UAS-TNT-V; active, Mz1369/UAS-TNT-H) alters medulla patterning in the midpupal Drosophila optic lobe.A, B, Horizontally sectioned, partial reconstructions of mAb nc82-stained optic lobes. The wild-type columnar organization of the medulla (me) is clearly recognizable after expression of inactive TeTxLC (A) but appears disturbed after expression of active TeTxLC (B). The overall shape of the neuropils is not altered. C, D, Medulla stainings of inactive and active TeTxLC-expressing optic lobes with anti-IrreC. As in wild type, expression of inactive TeTxLC produces a highly organized staining pattern of the distal (arrow) and proximal (arrowhead) medulla. A complete loss of columnar organization in the proximal medulla (9th layer) can be seen after active TeTxLC expression (D). E, F, Staining with anti-FasII shows arborizations of Fasciclin II-positive lamina monopolar cells in the distal medulla. The wild-type pattern of arborizations is observed after inactive TeTxLC expression (E). After active TeTxLC expression the arborizations appear disorganized and show overlaps (F). G, H, Staining with anti-chaoptin shows R7 and R8 photoreceptor axons and terminals in the distal medulla. Arborizations are formed in the distal medulla (arrow), and R7 terminals can be addressed in the sixth medulla layer (arrowhead). These arborizations appear regular after expression of inactive TeTxLC (G) and exhibit broader extensions and more overlaps (arrowhead) after expression of active TeTxLC (H). Scale bars: (in A)A, B, 50 μm; (in C, E, G)C–H, 20 μm.