Lateral adherens junctions mediate a supracellular actomyosin cortex in drosophila trachea.

Drosophila trachea is a classical model for analyzing epithelial, especially tubular epithelial biology. We identify lateral E-cadherin mediated junctions that encircle the cells just basal to the zonula adherens in the larval trachea. The lateral junction is associated with downstream adapters, including catenins, and has a distinct junctional actin cortex. The lateral cortex contributes to the development of a supracellular actomyosin mesh in the late larvae. Establishment of this cytoskeletal structure depends on lateral junction associated Rho1 and Cdc42 GTPases, and Arp and WASP pathways. The supracellular network takes the character of stress fibers along the AP axis in the early hours of pupation. It contributes to the shortening of the epithelial tube albeit in a manner redundant to ECM-mediated compression mechanism. In conclusion, we show the in vivo existence of functional lateral adherens junction and suggest a role for it in mediating dynamic cytoskeletal events during tissue scale morphogenesis.