Role of knot (kn) in wing patterning in Drosophila.

We have undertaken a genetic analysis of new strong alleles of knot (kn). The original kn1 mutation causes an alteration of wing patterning similar to that associated with mutations of fused (fu), an apparent fusion of veins 3 and 4 in the wing. However, unlike fu, strong kn mutations do not affect embryonic segmentation and indicate that kn is not a component of a general Hh (Hedgehog)-signaling pathway. Instead we find that kn has a specific role in those cells of the wing imaginal disc that are subject to ptc-mediated Hh-signaling. Our results suggest a model for patterning the medial portion of the Drosophila wing, whereby the separation of veins 3 and 4 is maintained by kn activation in the intervening region in response to Hh-signaling across the adjacent anterior-posterior compartment boundary.