Fig. 3. Babo is required in the developing larval brain lobes but not in eye discs for normal photoreceptor axon targeting in Drosophila. Ubiquitous expression (da>Gal4) of UAS-babo_b (A) but not the babo_a (B) isoform rescues the photoreceptor axon targeting and small brain phenotype of babo^26/52 mutants. (C) No rescue of photoreceptor axon targeting phenotypes of babo^26/32 mutants by the expression UAS-babo_a+b in eye discs (ey>Gal4 driver) or in glial cells (D, repo>Gal4). (E) babo⁵² homozygous mutant photoreceptor clones (GFP-negative) from an eye disc induced by ey>Gal4-UAS-Flp showed normal axon projections (red, anti-24B10) into a babo⁵² heterozygous brain lobe. Anti-Elav antibody labeled differentiated neurons (magenta). (F) Expression of the 1407 Gal4 driver in the brain lobe is highlighted in green (anti-β-gal) and neurons in red (anti-Elav). Note the lack of lacZ staining in the eye disc and prominent staining of central brain neuroblasts (arrowhead) and the OPCs. (G) Expression of both UAS-babo_a+b by the 1407 driver rescued the babo^26/32 mutant phenotype. Photoreceptor axons are in green (anti-24B10) and glia are in red (anti-Repo). (H) Expression of nuclear-GFP with the Wor>Gal4 driver is specific to neuroblasts and GMCs (arrowheads). Neurons are stained with Elav. Note the absence of GFP in the eye disc. The smaller OPC and IPC neuroblasts are not evident in this picture. (For additional images of Wor-Gal4 expression, see Fig. S3A-D in the supplementary material.) (I) Expression of both UAS-babo_a+b by the wor>Gal4 rescues the babo^26/32 mutant phenotype. Photoreceptor axons are in green (anti-24B10) and neurons in red (anti-Elav). ed, eye disc; la, lamina.