Tufted Is a Gain-of-Function Allele That Promotes Ectopic Expression of the Proneural Gene amos in Drosophila

摘要

The Tufted1 (Tft 1) dominant mutation promotes the generation of ectopic bristles (macrochaetae) in theuddorsal mesothorax of Drosophila. Here we show that Tft 1 corresponds to a gain-of-function allele of theudproneural gene amos that is associated with a chromosomal aberration at 36F–37A. This causes ectopicudexpression of amos in large domains of the lateral-dorsal embryonic ectoderm, which results in supernumeraryudneurons of the PNS, and in the notum region of the third instar imaginal wing, which gives rise toudthe mesothoracic extra bristles. Revertants of Tft 1, which lack ectopic neurons and bristles, do not showudectopic expression of amos. One revertant is a loss-of-function allele of amos and has a recessive phenotypeudin the embryonic PNS. Our results suggest that both normal and ectopic Tft 1 bristles are generatedudfollowing similar rules, and both are subjected to Notch-mediated lateral inhibition. The ability of Tft 1udbristles to appear close together may be due to amos having a stronger proneural capacity than that ofudother proneural genes like asense and scute. This ability might be related to the wild-type function of amosudin promoting development of large clusters of closely spaced olfactory sensilla.