Figure 1 : Cell rearrangement in the Drosophila melanogaster germband.

From: Polarize to elongate

Figure 1

a, Extension of the precursor to the trunk region, or germband, of fruit-fly embryos involves cell intercalation — cells that lie adjacent to one another along the anterior–posterior axis become separated as cells from above and below (those along the dorsal–ventral axis) move in between them. As a result, the germband elongates in the anterior–posterior direction. Paré et al.1 report that this elongation is mediated by Toll receptor proteins. b, A model for the role of Toll receptors in the germband. Interactions between different Toll receptors on adjacent cells may activate the Rho-GTPase signalling pathway (labelled Rho). At vertical contacts, Rho-GTPase signalling promotes the accumulation and activation of the myosin II protein and activation of the Diaphanous (Dia) protein, and it inhibits the Par3 protein, which then dissociates from vertical contacts. Par3 consequently accumulates at horizontal contacts, where it stabilizes adherens junctions.