Jia-Wen Zhang

The centriole is well recognized for its ninefold symmetry, with nine microtubule blades arranged in a barrel-like structure. However, these blades adopt diverse architectures across evolution, ranging from microtubule singlets to triplets, and the mechanisms governing this variation and its biological significance remain largely elusive. Here we found that in Drosophila male germline cells, routine conversion of microtubule doublets to triplets is impaired in the absence of Ana1. The Ana1 N-terminal region localizes adjacent to microtubule doublets and promotes modest elongation, whereas the C-terminal region extends outward and is sufficient to support C-tubule assembly. Ana1 recruits centrobin to centrioles via its C-terminal region, and targeted recruitment of centrobin to centrioles restores C-tubule formation in an Ana1-deficient background. Restoring Ana1 expression at different developmental stages reveals that the integrity of triplet microtubules is critical for male fertility. Together, these findings identify a regulator of centriolar doublet-to-triplet conversion and provide insights into the biological significance of this process.

Cilia, despite sharing a conserved axonemal structure, display diverse structural and molecular features, particularly at their tips. This study uncovers a mechanism that shapes the molecular features of fly mechanosensory cilia tips through localized active transport mediated by Kif19A, a kinesin-8 family member. Kif19A is predominantly expressed in peripheral neurons and is essential for enriching mechanosensory molecules at the ciliary tip, though it does not affect overall ciliary structure. In vitro studies show that Kif19A motors bind transiently to microtubules and exhibit non-processive movement individually, while multiple motors work together to drive plus end-directed movement of the cargoes, essential for precise localization and function of Kif19A in vivo. Building on the experimental observations, we propose a theoretical model in which nanoscale molecular polarity is established by local transport and binding sites that counteract rapid diffusion. This model highlights key principles by which molecular motors shape nanoscale cellular structures, thereby contributing to the diversity of cell architecture.