The alternative migratory pathways of the Drosophila tracheal cells are associated with distinct subsets of mesodermal cells

The Drosophila tracheal system is a model for the study of the mechanisms t hat guide cell migration. The general conclusion from many studies is that migration of tracheal cells relies on directional cues provided by nearby c ells. However, very little is known about which paths are followed by the m igrating tracheal cells and what kind of interactions they establish to mov e in the appropriate direction. Here we analyze how tracheal cells migrate relative to their surroundings and which tissues participate in tracheal ce ll migration. We find that cells in different branches exploit different st rategies for their mi,oration; while some migrate through preexisting groov es, others make their way through homogeneous cell populations. We also fin d that alternative mi,oratory pathways of tracheal cells are associated wit h distinct subsets of mesodermal cells and propose a model for the allocati on of groups of tracheal cells to different branches. These results show ho w adjacent tissues influence morphogenesis of the tracheal system and offer a model for understanding how organ formation is determined by its genetic program and by the surrounding topological constraints. (C) 2000 Academic Press.