Fig. 7. Amph and Bifocal act oppositely for proper rhabdomere development. (A-C) Transmission electron micrographs of genetic combinations of Bifocal and Amph. (A) amph²⁶/amph²⁶ mutant. The rhabdomeres are closely packed and occasionally fused (arrow). (B) bifocal^R38/bifocal^R38. As reported previously, bifocal mutants have split and elongated rhabdomeres. (C) bifocal^R38/Y; amph²⁶/+. Removal of one copy of amph results in a partial rescue of the bifocal phenotype. First actin localization appears normal (data not shown) and subsequently fewer rhabdomeres are split and elongated. (D-F) Optical sections through the developing retinal epithelium 55 hours APF of a bifocal mutant stained for Amph (green) and F-actin (red) (D) Amph expression in bifocal^R38/bifocal^R38. Amph localization in a bifocal mutant still demarcates the apical surface but is very diffuse rather than a tight crescent. (E) F-Actin expression in bifocal^R38/bifocal^R38. Like Amph, Actin still localizes to the apical surface but shows diffuse staining. (F) F-Actin still colocalizes with Amph, as seen in normal development.