Functional implications of the unusual spatial distribution of a minor α-tubulin isotype in Drosophila: A common thread among chordotonal ligaments, developing muscle, and testis cyst cells

Abstract

Three of the four α-tubulin genes in Drosophila melanogaster are temporally regulated. mRNA from one of these genes, α85E-tubulin, first appears in 6- to 8-hr embryos and persists, with marked fluctuations, through the end of pupal development. In adults, α85E mRNA has been unequivocally identified only in testes. In the present study, isotype-specific antibodies have been used to localize α85E tubulin protein in whole tissues. The results demonstrate a spatially restricted expression pattern of the α85E gene that includes tissues of both ectodermal and mesodermal origins. Specifically, embryonic accumulation of α85E tubulin is limited to support cells of chordotonal organs and the developing musculature of the viscera and body wall. In late third instar larvae, chordotonal organs and a subset of larval nerves, but not muscle, stain with anti-α85E. The timing of protein accumulation during pupal development suggests that α85E tubulin is involved in the construction of the adult as well as the larval musculature. In testis, only the somatically derived cyst cells that surround developing spermatid bundles accumulate α85E-tubulin. The cell types that express α85E share a requirement for extensive cell shape changes during development, suggesting that this minor α-tubulin may have distinct functional properties.