Endosome maturation and distribution during subcellular tube growth. (A and B) Terminal cells expressing FYVE::GFP (A' and B') and CD4::mIFP (A'' and B'') under btl-gal4. (A) Control. (B) Cells additionally expressing Vha100^R755A (V100^R755A). (C–E) Terminal cells expressing CD4::mIFP, Par3::YFP, and constitutively active FGFR, λbtl, under btl-gal4. (C’ and D’) CD4::mIFP. (C’’–E’’) Manual tracings of the cell contours (dark gray), subcellular tube (black), endosomes (red), and dorsal branch cells (light gray). Black and white arrowheads point to CD4 vesicles. Ventral is down.