Figure 6.

Intestinal microvilli are defective or absent from ACT-5–depleted animals. In wild-type ultrastructural preparations (a and c), intestinal cross sections reveal tightly packed, finger-like projections that correspond to microvilli projecting from the lumenal surface. At the base of these projections is an electron-dense region called the terminal web (TW). A small segment of the terminal web is enclosed by brackets in a and b. Two finger-like projections pointing toward the cytoplasmic side of the intestinal cells are the apical junctions (arrowheads) that mark the boundary between apical regions of two intestinal cells. Microvilli are absent from intestinal cross sections of act-5 (dt2017) animals (b). act-5(RNAi) animals frequently exhibited one shortened apical region (distance between apical junctions) on one of a pair of intestinal cells; this shortened apical surface was typically associated with an abnormally thick terminal web (d). Equivalent higher magnification views of a portion of the thick (e) and normal terminal web width (f) from the micrograph shown in d reveal the difference in thickness as the gap between the arrows (e and f). Control RNAi cross section from an L2–L3 stage animal shown in c. Bar for a and b in b; for c and d in d, 500 nm.