Quantitative analysis and modeling of katanin function in flagellar length control

Area of Science:

• Cell biology
• Organelle biogenesis
• Cytoskeletal dynamics

Background:

• Flagellar length control in Chlamydomonas reinhardtii serves as a model for organelle size regulation.
• Cellular precursor pools are sufficient for half-length flagella, with full-length assembly requiring additional precursor synthesis.
• Regulatory mechanisms governing precursor pool synthesis and regeneration remain largely unknown, though transcriptional control is implicated.

Purpose of the Study:

• To identify genes controlling flagellar precursor pool regeneration.
• To elucidate the molecular mechanisms underlying flagellar length control.
• To investigate the role of tubulin competition in flagellar assembly.

Main Methods:

• Quantitative analysis of flagellar length distributions to identify candidate genes.
• Genetic analysis of mutations affecting flagellar length, specifically in the PF15 gene.
• Stochastic simulation modeling to test hypotheses about tubulin pool competition.

Main Results:

• A mutation in the PF15 gene (encoding the p80 regulatory subunit of katanin) alters flagellar length by affecting precursor pool utilization kinetics.
• This suggests a model where flagella and cytoplasmic microtubules compete for a limited tubulin pool.
• Stochastic simulations confirmed that competition for tubulin can explain the observed effects of pf15 mutations on flagellar length.

Conclusions:

• Katanin, via its p80 subunit, plays a role in flagellar length control by influencing tubulin pool accessibility.
• Cytoplasmic microtubules compete with flagella for available tubulin precursors.
• Modulating microtubule severing dynamics can impact flagellar length, highlighting the interplay between different cytoskeletal structures.