Fig. 1.

Loss of PIP4K leads to the formation of expanded endomembranes under illumination. (A,B) TEMs showing transverse sections of PRs from control (Ai) and PIP4K²⁹ (Aii) pupae during late (90%) pupal development (pd) reared in the dark; and control (Bi), PIP4K²⁹ (Bii–iv), Rh1>PIP4K; PIP4K²⁹ (Bv) Rh1>PIP4K PRs (Bvi) reared under illumination. The white arrowheads indicate endosome-like vesicles (labelled E) and black arrowheads indicate the MVBs, both of which are expanded in PIP4K²⁹ PRs under illumination (Bii–iv). R7, R7 PR cell. (C) Immuno-gold labelling for Rh1 in WT (i) and PIP4K²⁹ PRs (ii). Arrows point to immunogold particles labelling Rh1, which are mostly present in the rhabdomere or apical plasma membrane (APM) in WT and in cytosolic endosome-like vesicles in PIP4K²⁹ PRs. Scale bars: 1 μm. (D) Volume fraction analysis (VFA) for endosome-like vesicles in control, PIP4K²⁹ and Rh1>PIP4K; PIP4K²⁹ PRs under illumination at 90% pupal development. (E) VFA for MVBs under illumination at 90% pupal development. The values indicate the mean±s.e.m. of volume fraction in arbitrary units. *P<0.05; ***P<0.001 (one-way ANOVA with a nonparametric with Kruskal–Wallis test and Dunn's post test to compare the variance across samples).