THE GENE POXN CONTROLS DIFFERENT STEPS OF THE FORMATION OF CHEMOSENSORY ORGANS IN DROSOPHILA

The gene poxn codes for a transcriptional regulator that specifies pol y-innervated (chemosensory), as opposed to mono-innervated (mechanosen sory), organs in Drosophila. The ectopic expression of poxn during met amorphosis results in a transformation of the morphology and central p rojection of adult mechanosensory organs toward those of chemosensory organs. Here we show, by electron microscopy analysis of normal and tr ansformed bristles and by Dil labeling of the innervating neurons, tha t poxn also controls the number of neurons. To determine whether poxn can transform not only the sense organ precursor cells but also their daughter cells, we examine the effects of the ectopic expression of po xn at different stages of the lineage, and we conclude that poxn can a ct at a late stage to affect the fate of the undifferentiated neuron.