TRANSCRIPTION OF THE BETA-1 TUBULIN (BETA-TUB56D) GENE IN APODEMES ISSTRICTLY DEPENDENT ON MUSCLE INSERTION DURING EMBRYOGENESIS IN DROSOPHILA-MELANOGASTER

The insertion of the somatic musculature into the epidermis during emb ryogenesis of Drosophila melanogaster represents an excellent system f or the investigation of cell-cell communication processes. Evidence fr om earlier experiments suggested that the expression of the beta 1 tub ulin gene from D. melanogaster in the epidermal attachments may be dep endent upon myotube insertion. Analysis of the transcription of the be ta 1 tubulin gene in mutants for pair-rule or segment polarity genes r evealed strong coupling of the induction process to myotube insertion. Involvement of extracellular matrix proteins of the integrin family c ould be excluded since beta 1 mRNA is detectable in the apodemes in mu tants for the common subunit PSbeta until muscles detach late in embry ogenesis. Furthermore, the lack of specific muscles in the myogenic mu tants rolling stone (rost) and not enough muscles (nem) eliminates bet a 1 transcription exclusively in the corresponding apodemes. The data presented clearly show that the transcription of the beta 1 tubulin ge ne in the muscle attachment sites is activated by myotube insertion by a yet unidentified pathway.