The centrosome is the primary microtubule-organizing center of the cell and is composed of a pair of centrioles surrounded by pericentriolar material (PCM). Microtuble assembly is initiated within the PCM and during M phase, these microtubules arrange to form the mitotic spindle. Precise duplication of the centrosome is critical for proper spindle assembly but the underlying mechanism is poorly understood. The
zyg-1 gene of C. elegans encodes an essential regulator of centrosome duplication. ZYG-1 is a protein kinase that localizes transiently to centrosomes and is specifically required for daughter centriole formation during early and late developmental stages. To identify additional components of the replication machinery we have identified and begun to analyze a set of suppressors of
zyg-1 embryonic lethality. We screened ~314,000 haploid genomes and have identified 48 suppressors. Nine of these are recessive while the remainder show some degree of dominance. Genetic mapping indicates that these suppressors comprise at least 4 loci one of which is linked to
zyg-1. Interestingly, one of these suppressors,
bs7, exhibits a temperature-sensitive embryonic lethal phenotype in the presence of wild-type
zyg-1. At 25, embryos produced by
bs7 hermaphrodites exhibit defects in centrosome number and microtubule organization, indicating that the gene defined by
bs7 plays an important role in centrosome duplication. Further analysis of these suppressor should provide significant insight into the mechanism regulating centrosome duplication.