Wingless modulates the effects of dominant negative notch molecules in thedeveloping wing of Drosophila

The development and patterning of the wing in Drosophila relies on a sequen ce of cell interactions molecularly driven by a number of ligands and recep tors. Genetic analysis indicates that a receptor encoded by the Notch gene and a signal encoded by the wingless gene play a number of interdependent r oles in this process and display very strong functional interactions. At ce rtain times and places, during wing development, the expression of wingless requires Notch activity and that of its ligands Delta and Serrate. This ha s led to the proposal that all the interactions between Notch and wingless can be understood in terms of this regulatory relationship. Here we have te sted this proposal by analysing interactions between Delta- and Serrate-act ivated Notch signalling and Wingless signalling during wing development and patterning. We find that the cell death caused by expressing dominant nega tive Notch molecules during wing development cannot be rescued by coexpress ing Nintra. This suggests that the dominant negative Notch molecules cannot only disrupt Delta and Serrate signalling but can also disrupt signalling through another pathway. One possibility is the Wingless signalling pathway as the cell death caused by expressing dominant negative Notch molecules c an be rescued by activating Wingless signalling. Furthermore, we observe th at the outcome of the interactions between Notch and Wingless signalling di ffers when we activate Wingless signalling by expressing either Wingless it self or an activated form of the Armadillo. For example, the effect of expr essing the activated form of Armadillo with a dominant negative Notch on th e patterning of sense organ precursors in the wing resembles the effects of expressing Wingless alone. This result suggests that signalling activated by Wingless leads to two effects, a reduction of Notch signalling and an ac tivation of Armadillo. (C) 1999 Academic Press.