Tissue localization of Drosophila melanogaster ras transcripts during development.

Three ras homologs have been identified in Drosophila melanogaster. Here we describe the tissue distribution of their transcripts as analyzed by in situ hybridization. The RNAs of the three genes show a similar distribution at every developmental stage examined. In embryos, the transcripts are uniformly distributed. In larvae, ras transcripts are restricted to dividing cells (e.g., imaginal disks, gonads, and brain). At the adult stage, several tissues contain ras transcripts. The strongest hybridization signals are localized to the adult ovaries and to the cortex of the brain and ganglia, which at this stage are comprised of differentiated, nondividing cells. The tissue distribution of ras transcripts in D. melanogaster suggests that the ras proteins have multiple roles during development which may be related to both the proliferative and differentiated states of the tissues.