The post-translational modification (PTM) of microtubules is thought to locally control microtubule dynamics, microtubule-based transport and the binding of microtubule-associated proteins. Neuronal microtubules are highly enriched in a number of PTMs, including acetylation, but it is unclear whether and how microtubule acetylation might sculpt neuronal architecture; it is also unknown whether microtubule acetylation has a role in dendrite morphogenesis. Now (p. 4120), Jill Wildonger and colleagues use targeted mutagenesis to examine the role of microtubule acetylation in neuronal transport and morphogenesis in Drosophila. To facilitate their studies, the authors create a new fly strain that enables them to knock-in alleles of the predominant α-tubulin-encoding gene in flies, αTub84B. The authors find loss of microtubule acetylation, polyglutamylation and (de)tyrosination do not affect animal survival. Acetylation-blocking mutations, however, do disrupt the refinement of sensory dendrite branches. Targeted mutagenesis of α-tubulin lysine 40 (K40) also affects microtubule growth, lysosome transport and the distribution of Futsch, a microtubule-associated protein, in dendrites but not axons. These data suggest a novel function for α-tubulin K40 and microtubule acetylation in fine-tuning the terminal dendrite branches of developing sensory neurons.