Figure 1

eve1 expression in relation to the movement of tissues during stages 3 to 4.2. Embryos are aligned from top to bottom according to developmental age, indicated by the number of the last formed leg-bearing segments (LBS). The left column shows embryos stained for dpp, in lateral view, head on the left, ventral side at the bottom (A, C, E, G). The three columns on the right show the expression of eve1 (B, D, F, H); on each row the same embryo is viewed (1) laterally with florescent nuclear staining (SYBR green), (2) in normal light from the same view, and (3) from a posterior orthogonal view. Primary rings of eve1 expression surround the proctodeum (black asterisk). Numbers marking the primary rings indicate the LBS number to which each ring will eventually give rise. Primary rings (and intercalated eve1 stripes) are compressed and bent by the extension of the germ band around the egg and by the reduction of the terminal disc. The forward expansion of the rings is associated with a contraction of the whole egg epithelium towards the cephalic region of the germ band. This is shown by the movement of the dpp stripes which persist at double segment periodicity throughout the extra-embryonic region and move with associated morphological segments. Magenta arrowhead marks the second LBS; red arrowhead marks the associated ring of dpp (A, C, E, G) or eve1 (B2). The last resolved eve ring in embryo B is that corresponding to the 20^th LBS (numbered black arrowhead). The location of this ring/stripe in embryos D, F and H is marked with a black arrowhead. The most recently resolved eve ring in these embryos is numbered. Black arrow: first appearance of intercalating single segment periodicity eve1 stripe; red asterisk: broken epithelium . Scale bar: 400 μm.