Cytokinesis in Saccharomyces cerevisiae can occur via the contraction of an actomyosin ring or through septum formation. Although the actomyosin contractile ring is not essential, S. cerevisiae strains deleted for hofl, a gene important for septum formation, are dependent on the actomyosin contractile ring for cytokinesis and viability (Vallen et al. 2000). A screen for mutants synthetically lethal with hofl was utilized to identify genes required for the function of the actomyosin pathway. Forty-one HOFl - dependent mutants were identified by screening 33,000 mutagenized colonies using a sectoring assay and other genetic tests.\ud
Genetic analysis suggests that the 34 recessive mutants fall into 18 complementation groups, 11 of which are single alleles. Seven mutants have dominant mutations or exhibit unlinked non-complementation; it is not yet known how many loci this represents. Complementation testing and plasmid-linked suppression indicates that three of the complementation groups are MYOl, BNIl, and CYK3. Interestingly, some of the myol and cyk3 mutants appear to exhibit unlinked non-complementation. Phenotypic analysis including Hoechst staining of DNA, rhodamine-phalliodin staining of the actin cytoskeleton, DIC microscopic analysis, and zymolyase treatment was used to characterize mutants. Results indicate that four mutants that may affect the actin-myosin pathway and cytokinesis are worthy of further analysis
