Functions of CRK1 Gene of Candida albicans as Studied by Gene Knock-out.

In the course of screening MAPK related protein kinase genes from Candida albicans DNA library, a CRK1 (CDC2-related protein kinase) gene was identified. Deletion of the CRK1 gene significantly decreased the growth. rate of cells. CRK1 knock out strains precipitated more rapidly in YPD liquid medium. The CRK1 null mutant stimulated hyphae formation in Lee's liquid medium at pH 4.5 and 25 degrees, which is the medium that maintains the wild type Candida albicans strain in yeast form. These phenomena suggest that CRK1 gene may be involved in cell cycle, flocculation and morphogenesis of Candida albicans. Overexpression of the half length CRK1 gene could induce the invasive growth into agar faintly, the cells that was capable of the invasive growth also changed their cell shapes to long, thin pseudohyphal-like cells, but the full-length CRK1 had only weak effect. The Crk1p might promote the invasive growth or cell elongation through a route different from the MAPK signal transduction pathway.