Saccharomyces cerevisiae mata mutant cells defective in pointed projection formation in response to α‐factor at high concentrations

Abstract

We have isolated Saccharomyces cerevisiae MATa mutant cells that do not form a pointed projection but elongate in response to alpha-factor at high concentrations. Complementation tests defined three genes, PPF1, PPF2, and PPF3 (for pointed projection formation), necessary for pointed projection formation. Allelism tests with genes known to be needed for projection formation revealed that PPF1 is identical to SPA2, while PPF2 and PPF3 are not allelic to SST2, STE2, SPA2, BEM1 or SLK1/SSP31/BCK1. The morphology of MATa ppf mutants treated with high concentrations of alpha-factor is similar to that of MATa PPF cells treated with alpha-factor at low concentrations. Quantitative mating tests showed that PPF2 and PPF3 are not essential for mating in either MATa or MAT alpha background. Monitoring of division arrest and expression of an alpha-factor-inducible gene revealed that mutations in the PPF genes do not affect the responses of MATa cells to low concentrations of alpha-factor. Unlike wild-type cells, the ppf mutants exhibited early recovery from alpha-factor-induced division arrest. Furthermore, vegetatively growing ppf3-1 cells are slightly defective in cell separation of mother and daughter cells and in selection of the correct bud sites in all cell types. These results indicate that PPF2 and PPF3 are involved in the response to alpha-factor at high concentrations and that PPF3 is also required for proper establishment of polarity in vegetative growth.

Expression deconvolution: A reinterpretation of DNA microarray data reveals dynamic changes in cell populations

“…Deconvolution reveals that cln3⌬ cells show roughly equal proportions of G 1 and S phase cells, but no other phases. For each of the other strains, the observed deconvolution results match the defects observed by other techniques (17)(18)(19)(20)(21), such as the known post-S phase delay of cells overexpressing calmodulin [CMD1 (Tet)], which are defective in nuclear division (22), exhibiting a higher proportion of M and M͞G 1 cells in our analysis.…”

“…The bud14⌬, she4⌬, and rrm3⌬ strains show excess 1N cells (relative to the wild-type cells derived from the same tetrads), similar to the defect seen in the known G 1 arrest mutant cka2⌬ (14). Likewise, the gas1⌬ mutant shows an excess of 2N cells, consistent with a post-S phase defect, just as does the M͞G 1 defective bni1⌬ strain (21).…”

“…5A, including four mutants whose deconvolution phenotypes indicated G 1 delay and two mutants exhibiting M͞G 1 delay. Two of the strains act as controls [cka2⌬ (14) and bni1⌬ (21)], in which the cell cycle delay phenotypes were known, and four represent previously undescribed cell cycle delay mutants.…”

Pea2 protein of yeast is localized to sites of polarized growth and is required for efficient mating and bipolar budding.

“…Mutants defective in one or both genes have identical shmoo and mating defects, which suggests that these genes may function in the same aspect of polarized morphogenesis during mating. Second, both genes were identified in an independent screen (Yorihuzi et al, 1994) for mutants defective in shmoo formation (PEA2 The Journal of CeU Biology, Volume 135, 1996is identical to PPF2; Dorer, R., and L. Hartwell, personal communication). Third, both genes are required for default mating in the absence of a pheromone gradient (Dorer et al, 1995; Dorer, R., and L. Hartwell, personal communication).…”

Spa2p Interacts with Cell Polarity Proteins and Signaling Components Involved in Yeast Cell Morphogenesis

“…The yeast protein Spa2p localizes to growth sites and is important for polarized morphogenesis (14,30,57,71,80,81,92). Spa2p can be found at the incipient bud sites of unbudded cells, the bud tips of small budded cells, the necks of cells undergoing cytokinesis, and the projection tips of mating cells.…”