Adhesion to a common ECM mediates interdependence in tissue morphogenesis in Drosophila

For organs to be functional, the cells and tissues that constitute them must effectively interact with each other and coordinate their behaviours. Halfway during Drosophila embryogenesis, two lateral epidermal sheets stretch to fuse at the dorsal midline; concomitant with this, the main tubes of the respiratory system also shift towards the dorsal side of the embryo. Here, we show that these two processes occur simultaneously and are coordinated by the adhesion of the epidermal sheets and a subset of cells of the tracheal trunks to a common extracellular matrix (ECM) that separates them. We show that during dorsal closure, tracheal trunk cells extend protrusions towards the ECM underneath the epidermis. These protrusions are under tension, suggesting they have a mechanical function. Additionally, perturbing adhesion between tracheal cells and the epidermis affects the development of both tissues. Altogether, our findings uncover a novel mechanism used for tissue coordination during development, one that is based on tissue adhesion towards a common ECM capable of transmitting forces across the embryo.