title: Quantitative analysis and modeling of katanin function in flagellar length control.
abstract: Flagellar length control in Chlamydomonas reinhardtii provides a simple model system in which to investigate the general question of how cells regulate organelle size. 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. The regulatory systems that control the synthesis and regeneration of this pool are not known, although transcriptional regulation clearly plays a role. 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. This finding suggests a model in which flagella compete with cytoplasmic microtubules for a fixed pool of tubulin, with katanin-mediated severing allowing easier access to this pool during flagellar assembly. 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.
authors.affiliation: Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA 94158.
authors.forename: Elisa
authors.initials: E
authors.lastname: Kannegaard
authors.affiliation: Graduate Group in Biophysics, University of California, San Francisco, San Francisco, CA 94158 Physiology Course, Marine Biological Laboratory, Woods Hole, MA 02543.
authors.forename: E Hesper
authors.initials: EH
authors.lastname: Rego
authors.affiliation: Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA 94158.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Schuck
authors.affiliation: Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA 94158.
authors.forename: Jessica L
authors.initials: JL
authors.lastname: Feldman
authors.affiliation: Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA 94158 Graduate Group in Biophysics, University of California, San Francisco, San Francisco, CA 94158 Physiology Course, Marine Biological Laboratory, Woods Hole, MA 02543 wallace.marshall@ucsf.edu.
authors.forename: Wallace F
authors.initials: WF
authors.lastname: Marshall
mesh_terms: D000251:Adenosine Triphosphatases / Q000235:genetics* / Q000378:metabolism; D020418:Algal Proteins / Q000235:genetics* / Q000378:metabolism; D016825:Chlamydomonas reinhardtii / Q000235:genetics* / Q000378:metabolism / Q000648:ultrastructure; D003198:Computer Simulation; D005407:Flagella / Q000235:genetics* / Q000378:metabolism / Q000648:ultrastructure; D005786:Gene Expression Regulation; D000074201:Katanin; D008870:Microtubules / Q000235:genetics / Q000378:metabolism / Q000648:ultrastructure; D015233:Models, Statistical; D053141:Organelle Size; D011498:Protein Precursors / Q000235:genetics* / Q000378:metabolism; D021122:Protein Subunits / Q000235:genetics* / Q000378:metabolism; D015398:Signal Transduction; D013269:Stochastic Processes; D014158:Transcription, Genetic; D014404:Tubulin / Q000235:genetics / Q000378:metabolism
chemical_list: D020418:Algal Proteins; D011498:Protein Precursors; D021122:Protein Subunits; D014404:Tubulin; D000251:Adenosine Triphosphatases; D000074201:Katanin