Quantitative analysis and modeling of katanin function in flagellar length control.
Bottom Line: Previous work demonstrated that Chlamydomonas cytoplasm contains a pool of flagellar precursor proteins sufficient to assemble a half-length flagellum and that assembly of full-length flagella requires synthesis of additional precursors to augment the preexisting pool.We used quantitative analysis of length distributions to identify candidate genes controlling pool regeneration and found that a mutation in the p80 regulatory subunit of katanin, encoded by the PF15 gene in Chlamydomonas, alters flagellar length by changing the kinetics of precursor pool utilization.We tested this model using a stochastic simulation that confirms that cytoplasmic microtubules can compete with flagella for a limited tubulin pool, showing that alteration of cytoplasmic microtubule severing could be sufficient to explain the effect of the pf15 mutations on flagellar length.
Affiliation: Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA 94158.Show MeSH
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Mentions: We next examined flagellar regeneration kinetics directly in this subclass of short-flagella mutants (Figure 2A). In all five of the candidate mutants, the regeneration curves plateau abruptly at a short length relative to wild type and in this sense are reminiscent of wild-type cells treated with protein synthesis inhibitors. Such might be the expected result for a mutant with defects in pool regeneration. However, the initial growth rate is slightly reduced compared with wild-type cells. This could indicate some pool-independent effect of the mutation, or it could indicate the presence of a reduced pool from the very beginning of the time course, unlike in wild-type cells, where the pool starts out at full capacity.
Affiliation: Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA 94158.