Dachsous-Fat signaling shapes the Drosophila wing through mechanical forces.

Proper organ shape is critical for function. The Drosophila wing normally adopts an elongated shape, but mutations in the Dachsous-Fat pathway result in rounder wings. The mechanism by which this occurs has remained unclear. Here, we show that Ds-Fat signaling shapes the wing during the larval stage, rather than during pupal development when morphogenetic rearrangements transform the developing wing disc into the adult wing. We further find that Ds-Fat alters tissue-wide stresses in the wing disc, and genetic manipulations that reduce cytoskeletal tension result in rounder wings, whereas increasing cytoskeletal tension produces more elongated wings. Reduced tension is also associated with less oriented growth during development. Notably, increased cytoskeletal tension partially rescues the rounder shape caused by ds knockdown. These results reveal a previously unrecognized mechanism by which Ds-Fat signaling determines wing shape, involving regulation of tissue tension to orient growth and shape the wing primordia during larval development.