ABSTRACT
During Drosophila embryogenesis, the β1 tubulin gene ( Tub56D) is expressed in the CNS and PNS as well as in the apodemes. In this report we determine the regulation of β1 tubulin gene expression during formation of the attachment sites of the somatic muscles, the apodemes. The process was analysed in transgenic flies carrying β1 enhancer-hsp70 promoter-lacZ fusion constructs. Expression is first detected at late stage 13 and remains until hatching. By deletion analysis of the intron we identified a 14-bp element present in three copies. This element represents a classical enhancer, as it acts on a heterologous promoter. Separate fragments containing the respective elements yield nearly identical expression patterns, and no cooperativity was observed between the three copies. Thus, the expression of the β1 tubulin gene in the apodemes is under control of redundant enhancer elements. Double staining for β1 tubulin gene expression in apodemes and for β3 tubulin gene expression in muscles allowed us to correlate apodeme and muscle formation. Cells of the apodemes that are in contact with their corresponding muscles show expression of the reporter gene as monitored by antibody staining.
