Katanin knockdown supports a role for microtubule severing in release of basal bodies prior to mitosis in Chlamydomonas

MQR and JDKP contributed equally to this work and are co-first authors. ABSTRACT Katanin is a microtubule-severing protein that participates in the regulation of cell cycle progression and in ciliary disassembly, but its precise role is not known for either activity. Our data suggest that in Chlamydomonas, katanin severs doublet microtubules at the proximal end of the flagellar transition zone, allowing disengagement of the basal body from the flagellum prior to mitosis. Using an RNAi approach we have discovered that severe knock-down of the p60 subunit of katanin, KAT1, is achieved only in cells that also carry secondary mutations that disrupt ciliogenesis. Importantly, we observed that cells in the process of cell cycle-induced flagellar resorption sever the flagella from the basal bodies before resorption is complete and we find that this process is defective in KAT1 knock-down cells.