Fig. 3
Generation and expression of the DRxGal4 strain. A The genomic organization of the DRx locus is shown with the positions of the six exons specific for the transcript variant DRx1 [6]. Noncoding regions are indicated by white boxes, and coding regions are indicated by blue boxes. The location of fragments used for the later analysis of enhancer activities is also indicated. B The genomic organization of the DRxGal4 strain is shown. Here, the region upstream of the ATG in exon 1 up to sequences shortly downstream of the exon 1 donor splice site has been deleted and replaced by Gal4 (yellow) flanked by an attP/B site (red) and a loxP site (green). C-G Laser confocal images showing the expression of the DRxGal4 strain in different developmental stages visualized using a UAS-H2B-mRFP1 strain and a UAS-mCD8::GFP strain. C In a stage 16 embryo (the anterior end of the embryo is pointing downward), DRx expression is shown in green and DRxGal4 dependent marker RFP expression is shown in red. Strong coexpression of the nuclear markers RFP and DRx can be observed in the embryonic brain and clypeolabrum (CL) (yellow arrowheads). D In the right hemisphere of a third instar larval brain, DRx and DRxGal4 marker coexpression in the type II lineages (DM, DL) is shown (yellow arrowheads). In the medulla (M), only the RFP marker is expressed (red arrowhead). E Coexpression in the DM lineages is also visible using GFP as a marker (yellow arrowhead); in the medulla, again only GFP is expressed. F, G Additionally, in the adult brain, coexpression of DRx and RFP is detectable in an anterior focal plane (F) and a posterior focal plane (G) in most regions (yellow arrowheads) except for the protocerebral bridge, here more RFP marker expression is visible (red arrowheads) Abbreviations: AL, antennal lobe; LH, lateral horn; OL, optic lobe; OTU optic tubercle; PB, protocerebral bridge; PLP, posterior-lateral protocerebrum; SMP, superior-medial protocerebrum; VMC, ventro-medial cerebrum; VLP, ventro-lateral protocerebrum. G The RFP marker expression of the DRxGal4 is also apparent in living flies in the clypeus (red arrowhead), a structure that is missing in DRx mutants [7]. (Scale bars: C, 25 μm; D-F, 50 μm; G, 100 μm)