CILIA: NEW INSIGHTS INTO AN OLD ORGANELLE

Cilia and flagella are evolutionarily conserved organelles that are present across the eukaryotic phylogeny. The cilia play major roles in motility, development, and sensing. Consequently, cilia dysfunction is associated with a large group of clinically and genetically heterogeneous human diseases, known as ciliopathies. The axoneme, a microtubule-based structure, provides a scaffold for the cilium and plays a fundamental role in the ciliary organization and function. Thus, proper assembly of the axoneme is critical for the formation of the cilium and abnormal assembly may affect its function. We used the unicellular biflagellate green alga Chlamydomonas reinhardtii to understand how the stable structure of the axoneme can be assembled by intrinsically highly dynamic building blocks as tubulin, which constitutes the microtubules. To this end, we have developed a unique procedure to differentially extract tubulins from different components of axonemes (see Figure) and characterized their dynamic properties using Interference Reflection Microscopy (IRM). We identified two distinct mechanisms that allow axonemal tubulin to support the length stability of the axoneme. Furthermore, we found that post-translational modification has no significant effect on the dynamic properties of the tubulin.