Transcription of the beta 1 tubulin (beta Tub56D) gene in apodemes is strictly dependent on muscle insertion during embryogenesis in Drosophila melanogaster.

The insertion of the somatic musculature into the epidermis during embryogenesis of Drosophila melanogaster represents an excellent system for the investigation of cell-cell communication processes. Evidence from earlier experiments suggested that the expression of the beta 1 tubulin gene from D. melanogaster in the epidermal attachments may be dependent upon myotube insertion. Analysis of the transcription of the beta 1 tubulin gene in mutants for pair-rule or segment polarity genes revealed strong coupling of the induction process to myotube insertion. Involvement of extracellular matrix proteins of the integrin family could be excluded since beta 1 mRNA is detectable in the apodemes in mutants for the common subunit PS beta until muscles detach late in embryogenesis. Furthermore, the lack of specific muscles in the myogenic mutants rolling stone (rost) and not enough muscles (nem) eliminates beta 1 transcription exclusively in the corresponding apodemes. The data presented clearly show that the transcription of the beta 1 tubulin gene in the muscle attachment sites is activated by myotube insertion by a yet unidentified pathway.