During Drosophila embryogenesis the β1 tubulin gene is specifically expressed in the nervous system and the apodemes

Abstract

We determined the in vivo distribution of the β1 tubulin from D. melanogaster using isotype specific antibodies. Maternally expressed β1 tubulin is incorporated into mitotic spindles. Later in development a strong expression in the CNS is observed. Furthermore, all chordotonal organs and the apodemes are marked by β1 tubulin. Nuclear run-on assays and stage specific in vitro transcription showed a zygotic expression of the β1 tubulin gene from the extended germ-band stage onwards. Using the P-element system, we identified several elements; upstream between −2.2 kb and the transcription initiation site, elements for low level expression in the CNS are present. In the intron between +0.44 kb and +2.5 kb enhancer elements are located that drive the expression in the chordotonal organs and the apodemes. Between the start site and +0.44 kb (273 bp) and +2.5 kb and the second exon (315 bp), maternal and CNS enhancers result in full level expression of a lacZ-β1 reporter gene. We show, that the β1 tubulin gene is a very early effector gene starting its expression shortly after the commitment of neuroblast cell fate. This gene offers an excellent model system for the identification of neural and apodeme specific transcription factors.