The Noncell Autonomous Requirement of Proboscipedia for Growth and Differentiation of the Distal Maxillary Palp during Metamorphosis ofDrosophila melanogaster

TheDrosophilamaxillary palpus that develops during metamorphosis is composed of two elements: the proximal maxillary socket and distal maxillary palp. The HOX protein, Proboscipedia (PB), was required for development of the proximal maxillary socket and distal maxillary palp. For growth and differentiation of the distal maxillary palp, PB was required in the cells of, or close to, the maxillary socket, as well as the cells of the distal maxillary palp. Therefore, PB is required in cells outside the distal maxillary palp for the expression, by some mechanism, of a growth factor or factors that promote the growth of the distal maxillary palp. Bothwingless (wg)andhedgehog (hh)genes were expressed in cells outside the distal maxillary palp in the lancinia and maxillary socket, respectively. Bothwgandhhwere required for distal maxillary palp growth, andhhwas required noncell autonomously for distal maxillary palp growth. However, expression ofwg-GAL4andhh-GAL4during maxillary palp differentiation did not require PB, ruling out a direct role for PB in the regulation of transcription of these growth factors.