LARVAL CHEMOSENSORY PROJECTIONS AND INVASION OF ADULT AFFERENTS IN THE ANTENNAL LOBE OF DROSOPHILA

We have studied the fate of olfactory afferents during metamorphic tra nsformation of Drosophila melanogaster. Intracellular labeling of affe rents from larval head chemosensilla suggests that the larval antennal lobe may be an olfactory target, whereas tritocerebral and suboesopha geal centers are likely targets of gustatory sensilla, Application of monoclonal antibody 22C10 shows that the larval antennal nerve is the precursor of the adult antennal nerve and is used as a centripetal pat hway for the adult afferents, Likely guidance cues are larval olfactor y afferents that persist during early metamorphosis, P[GAL4] enhancer trap lines are introduced as efficient markers to follow the establish ment of adult sensory projections, beta-Galactosidase and the bovine T AU protein mere used as reporter proteins, and their expression patter ns are compared, P[GAL4] lines MT14 and KL116 demonstrate that adult a ntennal afferents have arrived in the antennal lobe 24 h after puparia tion and extend to the contralateral lobe 6 h later, Line MT14 express es GALA mostly in basiconic sensilla and in certain trichoid sensilla, whereas KL116 is specific for trichoid and a small subset of basiconi c sensilla, In the antennal lobe, largely complementary subsets of glo meruli are labeled by the two lines, in agreement with the observation that particular types of sensilla project to particular target glomer uli, (C) 1997 John Wiley & Sons, Inc.