Dbf2 is essential for cytokinesis and correct mitotic spindle formation inCandida albicans

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We have characterized theDBF2gene, encoding a protein kinase of the NDR family inCandida albicans,and demonstrate that this gene is essential for cell viability. Conditional mutants were constructed by using theMET3promoter to analyse the phenotype of cells lacking this kinase. The absence of Dbf2 resulted in cells arrested as large-budded pairs that failed to contract the actomyosin ring, a function similar to that described for itsSaccharomyces cerevisiaeorthologue. In addition to its role in cytokinesis, Dbf2 regulates mitotic spindle organization and nuclear segregation as Dbf2-depleted cells have abnormal microtubules and severe defects in nuclear migration to the daughter cell, which results in a cell cycle block during mitosis. Taken together, these results imply that Dbf2 performs several functions during exit from mitosis and cytokinesis. Consistent with a role in spindle organization, the protein localizes to the mitotic spindle during anaphase, and it interacts physically with tubulin, as indicated by immunoprecipitation experiments. Finally,DBF2depletion also resulted in impaired true hyphal growth.

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