The making of a fusion branch in the Drosophila trachea.

Connection of epithelial tubes to generate a common network is a key step in the formation of tubular organs such as the tracheal respiratory and the vascular systems. However, it is not clear how these connecting tubes arise. Here we address this issue by studying the dorsal fusion branches in the Drosophila trachea, taking into account the morphology and contribution of each cell type on the basis of their individual labeling. Our results explain how a fusion branch forms and also illustrate the different nature of the two seamless tubes in the Drosophila trachea, generated by fusion and terminal cells respectively.