Distribution of microtubules containing post-translationally modified alpha-tubulin during Drosophila embryogenesis.

The distribution of microtubules (MTs) enriched in detyrosinated alpha-tubulin (Glu-tubulin) was studied in Drosophila embryos by immunofluorescence microscopy by using a monoclonal antibody (ID5) which was raised against a 14-residue synthetic peptide spanning the carboxyterminal sequence of Glu-tubulin (Wehland and Weber: J. Cell Sci. 88:185-203, 1987). While all MT arrays contained tyrosinated alpha-tubulin (Tyr-tubulin), MTs rich in Glu-tubulin were not found during early stages of development even by using an image intensification camera. Elevated levels of microtubular Glu-tubulin were first detected after CNS condensation in neurone processes. In addition, sperm tails, which remained remarkably stable inside the embryo until late stages of development, were decorated by ID5. This was in marked contrast to the distribution of microtubule arrays containing acetylated alpha-tubulin, which could already be detected during the cellular blastoderm stage. Additional experiments with taxol suggested that the absence of MTs rich in Glu-tubulin during early stages of development was not due to the rapid turnover rate of MTs, which would be too fast for alpha-tubulin to be detyrosinated. The possible significance of the differential detyrosination and acetylation of microtubules during development is discussed.