Is there a relationship between deflagellation and flagellar resorption?
Laura K. Hilton and Lynne M. Quarmby
Simon Fraser University, Vancouver, Canada
Chlamydomonas, like most other cells, reabsorbs its flagella prior to mitosis. The signals that trigger pre-mitotic resorption and the mechanisms by which it occurs are largely unknown. In collaboration with the Rosenbaum lab, we have recently shown that a severing event releases basal bodies from flagellar transition zones (TZs) prior to mitosis (see abstract by Parker et al.). This event involves the co-ordinated severing of the nine outer doublet microtubules, reminiscent of the severing event that mediates stress-induced deflagellation. Whereas pre-mitotic severing occurs proximal to the TZ, the site of stress-induced severing is distal to the TZ. Stress-induced severing is triggered by a calcium signal; one class of deflagellation-defective strains, the fa mutants, do not sever their axonemes in response to calcium. Although fa mutants are viable, we have previously reported that fa2 cells show a delay in cell cycle progression (Mahjoub et al., 2002). Taken together, these and other data (see Parker & Quarmby, 2003) suggest that some or all of the deflagellation genes might also regulate or execute the severing event associated with mitosis. Using live cell imaging, we now report surprising patterns of pre-mitotic flagellar loss by various deflagellation-defective strains. Our new model for the relationship between deflagellation and flagellar resorption will be presented.
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