Figure 1. The arrangement of epithelial cells differs between embryo and larva.
Anterior is to the left in all figures. (A and B) An embryo is shown in (A) and the pre-L3 (i.e., the new third instar epidermis developing under the second instar cuticle) in (B). The seven rows of pre-denticles are numbered and arrows indicate the ventral midline. The pre-denticles are labelled with utrp::GFP and the cell outlines with DE-cad::GFP (both in green). Posterior cells and pre-denticles (rows 1 in (A) and rows 0 and 1 in (B)) show red because en.GAL4 is driving expression of UAS.cherry::moesin in the entire P compartment. (C and D) Embryo (C) and pre-L3 (D). Pre-denticles labelled with utrp::GFP as above. The muscle-attaching tendon cells are marked by sr.GAL4 driving expression of UAS.cherry::moesin (red). In the embryo (C) sr.GAL4 marks the pre-denticles of rows 2 and 5, made by the two lines of tendon cells in the embryo. In the pre-L3 larva (D) note the actin palisades in the tendon cells that are labelled in both green and red. In the larva, no pre-denticles are made by these two lines of cells. (E and F) show the cuticular denticles of the L1 (E) and L3 (F) larvae. Scale bars are 10 µm. (G) Diagrams of the embryonic and larval ventral epithelium. The green numbers indicate rows of denticles in L1, the red numbers in L2 and L3. Their polarities are indicated. Note the many changes between embryo and larvae (see also Figure 2).