Cytoplasmic dynein couples mitosis and morphogenesis in Candida albicans.
Kenneth Finley, Judith Berman
Genetics, Cell Biology & Dev., University of Minnesota, 321 Church St SE, Minneapolis, MN, 55455, USA
As a budding yeast, the human pathogen C. albicans is indistinguishable from S. cerevisiae. Unlike S. cerevisiae, C. albicans also forms true hyphae, where nuclei migrate tens of microns before and after mitosis. We investigated this long distance migration using time-lapse fluorescence microscopy in wild-type hyphae and in hyphae lacking the heavy chain of cytoplasmic dynein. In WT hyphae, forward nuclear migration does not begin until after a septin ring has formed 10-15 microns into the hyphal tube. Forward migration then proceeds by iterative microtubule sliding events that lead to large spindle displacements. During anaphase, one SPB is retained near the septin ring, while spindle elongation pushes the other away from the ring. Furthermore, spindle pole bodies and mitotic spindles are perpetually moving as a result of MT interactions with the cortex. In the absence of Dyn1p, these movements are largely lost and forward nuclear migration occurs primarily as a result of spindle elongation and secondarily as a result of other MT dynamics. Nonetheless, these mechanisms are insufficient to translocate an early spindle to the septin ring. Analysis of free and SPB-bound MTs in WT and dyn1delta cells suggests that cytoplasmic dynein acts as a MT minus-end stability factor. These results, accompanied by morphologic changes in anculeate hyphal tip cells, demonstrate a role for cytoplasmic dynein in the coordination of mitosis and morphogenesis.
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