Intellectual merit. As evolutionally conserved cellular appendages, cilia and flagella are important in many aspects of cellular physiology and development. They are assembled and maintained by a motility process called intraflagellar transport (IFT), which is characterized as the rapid, bidirectional movement of large protein particles between the flagellar base and the distal tip of the flagellum. IFT machinery includes three key components: the IFT particle, the anterograde motors and the retrograde motor. In the anterograde direction from the flagellar base to the flagellar tip, IFT particles are transported by either the heterotrimeric kinesin-II motor alone or kinesin-II together with the homodimer OSM-3 motor. In the retrograde direction, IFT is powered by the motor protein cytoplasmic dynein 1b. This project addresses how IFT motility is regulated at the molecular level by using the model organism Chlamydomonas. The research focuses on IFT27 and IFT25, two candidate regulatory subunits of the IFT particle. IFT27 is a Rab-like small GTPase and essential for normal flagellar assembly. IFT25 is a phosphoprotein and directly interacts with IFT27. This project is aimed at identifying the key steps of IFT that are controlled by IFT27 and IFT25, and the proteins that regulate the IFT27 conformational switch. In addition, the functional significance of IFT25 phosphorylation on IFT motility will be investigated. The results of the research should be of great interest to the field of ciliogenesis in general, where detailed functional analysis of IFT particle proteins in the regulation of IFT motility has rarely been done. In addition, the results will potentially contribute to other fields with the involvement of cilia, such as development and reproductive biology.
Broader impacts. The undergraduate and graduate students involved in this project will receive training in cell biology, biochemistry, molecular biology and genetics. These developing scientists will present their research findings at conferences and publish their results in scientific journals. Moreover, this project will also increase regional educational activities such as science fairs to simulate the next generation to pursue science paths.
