Motile cilia protrude from the surface of eukaryotic cells. Organised in polarised arrays, cilia beat to create a fluid flow that is important for motility. Basal bodies (BBs) nucleate, orientate and position cilia at the cell cortex. Microtubules (MTs) and fibrous linkages attach BBs to the cell cortex and among each other for the correct organisation of cilia. In their Research Article, Chad Pearson and colleagues (Junker et al., 2019) employ EM tomography and light microscopy to investigate BB-associated MTs during assembly of BBs in Tetrahymena thermophila. The authors show that the MTs in BB appendages nucleate and elongate during maturation of BBs, and that these MTs are in contact with the cytoskeleton at the cell cortex. BBs and BB-associated MTs have post-translational modifications (PTMs), such as acetylation, glutamylation and glycylation, and the authors determine the localisation of these PTMs. They find that, whereas BB-associated MTs are both acetylated and glycylated, it is MT glyclylation that is important for MT length, and BB orientation and organisation – specifically in order to respond to forces that arise from rapid ciliary beating and for the attachment of BBs to the cell cortex. By contrast, mutants that disrupt the cortical cytoskeleton prevent BB attachment to the cortex and provoke disorganisation of BBs. Taken together, this work demonstrates a role for tubulin glycylation in BB and cilia positioning at the cell cortex.
