CHLAMYDOMONAS KINESIN-II-DEPENDENT INTRAFLAGELLAR TRANSPORT (IFT) - IFT PARTICLES CONTAIN PROTEINS REQUIRED FOR CILIARY ASSEMBLY IN CAENORHABDITIS-ELEGANS SENSORY NEURONS

We previously described a kinesin-dependent movement of particles in t he flagella of Chlamydomonas reinhardtii called intraflagellar transpo rt (IFT) (Kozminski, K.G., K.A. Johnson, P. Forscher, and J.L. Rosenba um. 1993. Proc. Natl. Acad. Sci. USA. 90:5519-5523), When IFT is inhib ited by inactivation of a kinesin, FLA10, in the temperature-sensitive mutant, fla10, existing flagella resorb and new flagella cannot be as sembled. We report here that: (a) the IFT-associated FLA10 protein is a subunit of a heterotrimeric kinesin; (b) IFT particles are composed of 15 polypeptides comprising two large complexes; (c) the FLA10 kines in-II and IFT particle polypeptides, in addition to being found in fla gella, are highly concentrated around the flagellar basal bodies; and, (d) mutations affecting homologs of two of the IFT particle polypepti des in Caenorhabditis elegans result in defects in the sensory cilia l ocated on the dendritic processes of sensory neurons. In the accompany ing report by Pazour, G.J., C.G. Wilk Wilkerson, and G.B. Witman (1998 . J. Cell Biol. 141:979-992), a Chlamydomonas mutant (fla14) is descri bed in which only the retrograde transport of IFT particles is disrupt ed, resulting in assembly-defective flagella filled with an excess of TFT particles. This microtubule-dependent transport process, IFT, defi ned by mutants in both the anterograde (fla10) and retrograde (fla14) transport of isolable particles, is probably essential for the mainten ance and assembly of all eukaryotic motile flagella and nonmotile sens ory cilia.