Fig. 5. Fmi localization is dynamic throughout development and is dependent upon fz. (A) Wild-type third instar eye disc immunostained with anti-Fmi (white arrowhead indicates an R4 cell with a high level of Fmi). (B) High-magnification images of areas a-d in A. (a) Fmi is localized to all membranes of nascent photoreceptors in developing ommatidial clusters. (b) By row 6, Fmi is prominent at the membranes of R3 and R4 (white arrow indicates contact between R3 and R4) and at the point of contact between R1/R7/R6 and R8. (c) By row 8, Fmi is enhanced in R4 and by row 10 appears in punctate structures (d). (C) Fmi localization is disrupted in eye discs homozygous for fz^KD4A (a null allele). (D) High-magnification images of areas a-d in C. (a) Fmi localization is unaffected ahead of the furrow (not shown) and in early ommatidial precursors. (b) Localization of Fmi is not affected at this stage. (c) Preferential accumulation of Fmi to R4 is abolished in the fz^KD4A background. (d) Vesicle morphology is disrupted, primarily in the number, size and position of Fmi-containing vesicles. Scale bar: 5 µm. Anterior to the right.