Genetic analysis of inducible sexual agglutination ability in the yeast Saccharomyces cerevisiae

Genetic regulation of the inducibility of sexual agglutination ability in the yeast Saccharomyces cerevisiae was studied. Detailed analysis of the degree of sexual agglutination was carried out; it showed that a greater number of genes are involved in the regulation of inducible sexual agglutination in strain H1-0 than previously assumed. Although dominancy of inducible phenotype over constitutive was confirmed, the effectiveness of one gene changing the constitutive phenotype to the inducible seemed to be somewhat low. Quantity per cell of agglutination substances responsible for sexual agglutination increased as the agglutination ability became greater.     

Microtiter plate assay for sexual agglutination in the yeast Hansenula wingei.

A fast method is described for determining the mating type of yeast spore clones independent of genetic complementation between auxotrophic markers.     

Intra- and intergeneric mating behaviour of ascosporogenous yeasts I. Quantitative analysis of sexual agglutination

When respective opposite mating types of the heterothallic yeastsare mixed, remarkable sexual agglutination occurs. This is consideredto be indispensable for the subsequent cell fusion and karyogamy.Based on the Duysens's findings (1956) that the heterogeneousdistribution or localization of pigment in particles causedto flatten their absorption spectrum, we developed the followingequation to express the intensity of agglutination: I/flattening coefficient (designated agglutination index, A.I.) expresses mean value of aggregateradii as a parameter to express agglutination intensity. TheA.I. is easily measurable with a spectrophotometer. The bestfit of k with the experimental values was calculated with acomputer. The other parameter to express the intensity of agglutination,mean cell number per aggregate (N?), was roughly estimated bythe equation, The analysis of this parameter supported the above relationship between A.I.and . The approximations of the relationship between A.I. and are also presented and their validity is discussed. ¹ A part of this work was reported in Japanese in Ref. (24). (Received June 9, 1978; )     

The sexual agglutination substance is secreted through the yeast secretory pathway in Saccharomyces cerevisiae

Molecular Genetics and Genomics - A Saccharomyces cerevisiae a strain carrying the secretory mutation sec1, sec7 or sec18 showed no sexual agglutination ability when treated with α pheromone...     

The mating reaction in yeast

Summary Illegitimate / diploids heterozygous for the dmt gene, described previously, have been created and analyzed with respect to auxotrophic markers on chromosome III. It has been shown that in a high proportion of these diploids, which were theoretically heterozygous for the chromosome III auxotrophic markers his₄, leu₂ and thr₄, the expected dominant phenotype was not obtained. This non-expression of the dominant gene (NEDG) appears to be a result of modification of the chromosome III genes found in dmt containing strains. The dmt gene is thought to affect the mating type locus located 22 centermorgans from the centromere on chromosome III. Thus a closely linked antibiotic resistance marker for cryptopleurine was examined along with the auxotrophic markers located on other parts of chromosome III. Control experiments gave the expected expression of cryptopleurine resistance or sensitivity whereas / diploids heterozygous for the dmt gene once again showed non-expression of the dominant genotype for this mating type linked marker. A number of these diploids also showed the unexpected ability to sporulate and gave rise to either two or four viable spores per ascus. Our results are consistent with the idea that the dmt gene causes deletions on chromosome III, and this in turn alters the mating properties of the haploid cells. By observing the effects of various deletions in samples selected for mating dynfunction, it is possible to speculate on certain properties of mating regulation.     

The sexual agglutination substance is secreted through the yeast secretory pathway in Saccharomyces cerevisiae

Summary A Saccharomyces cerevisiae a strain carrying the secretory mutation sec1, sec7 or sec18 showed no sexual agglutination ability when treated with pheromone at the restrictive temperature 36° C, although the a agglutination substance had accumulated in the cytoplasm. These cells became sexually agglutinable, with a concomitant decrease in the agglutination substance in the cytoplasm, when the temperature was shifted from 36° C down to the permissive temperature 24° C after the addition of, cycloheximide. The a agglutination substance was barely detectable in sec53 cells (a) treated with pheromone at 36° C, indicating that the active a agglutination substance was formed after the export of its precursor into the endoplasmic reticulum. These results indicate that the a agglutination substance is exported through the yeast secretory pathway and that pheromone acts at the level of synthesis of the precursor molecule of the substance. An strain carrying sec1, sec7 or sec18 behaved just like an a strain carrying the sec gene in the induction of agglutination ability by the opposite mating type sex pheromone.     

Mating reaction inSaccharomyces cerevisiae VIII. Mating-type-specific substances responsible for sexual cell agglutination

The agglutination factors ofa and α mating types ofSaccharomyces cerevisiae were solubilized from isolated cell-wall fractions by treatment with snail enzyme (Glusulase) and shown to be adsorbed specifically by cells of the opposite mating type, resulting in the loss of agglutinability of these cells. The agglutination factors ofa and α types adsorbed by cells of the opposite mating type at pH 5.5 were eluted at pH 9.0. These factors were further purified on Sepharose 4B. From the elution pattern on Sepharose 4B, the molecular weights of the solubilized agglutination factors are estimated to be about one million. Thus purified agglutination factors contained carbohydrate and protein and were considerably resistant to heat treatment. Neutral protease ofBacillus subtilis inactivated botha and α type agglutination factors. Trypsin inactivated the α type agglutination factor only.     

Roles for receptors, pheromones, G proteins, and mating type genes during sexual reproduction in Neurospora crassa

Here we characterize the relationship between the PRE-2 pheromone receptor and its ligand, CCG-4, and the general requirements for receptors, pheromones, G proteins, and mating type genes during fusion of opposite mating-type cells and sexual sporulation in the multicellular fungus Neurospora crassa. PRE-2 is highly expressed in mat a cells and is localized in male and female reproductive structures. Δpre-2 mat a females do not respond chemotropically to mat A males (conidia) or form mature fruiting bodies (perithecia) or meiotic progeny (ascospores). Strains with swapped identity due to heterologous expression of pre-2 or ccg-4 behave normally in crosses with opposite mating-type strains. Coexpression of pre-2 and ccg-4 in the mat A background leads to self-attraction and development of barren perithecia without ascospores. Further perithecial development is achieved by inactivation of Sad-1, a gene required for meiotic gene silencing. Findings from studies involving forced heterokaryons of opposite mating-type strains show that presence of one receptor and its compatible pheromone is necessary and sufficient for perithecial development and ascospore production. Taken together, the results demonstrate that although receptors and pheromones control sexual identity, the mating-type genes (mat A and mat a) must be in two different nuclei to allow meiosis and sexual sporulation to occur.     

Evolution of mating preference and sexual dimorphism

A quantitative genetic model of the joint evolution of female mating preferences and sexual dimorphism in homologous characters of the sexes is described for polygamous species with no male parental effort, such that mating preferences are selectively neutral and evolve only by indirect selection on genetically correlated characters. The male character and the homologous female character are each under stabilizing natural selection toward an optimum phenotype. At an evolutionary equilibrium the female character under natural selection is at its optimum, whereas there is a line of possible equilibria between female mating preferences and the male character. The line of equilibria may be stable or unstable, depending on the intensity of natural selection, the type of mating preferences, and the inheritance of the characters. Various mechanisms for maladaptive evolution of mating preferences and sexual dimorphism are discussed.     

Dynamic studies of scaffold-dependent mating pathway in yeast

The mating pathway in Saccharomyces cerevisiae is one of the best understood signal transduction pathways in eukaryotes. It transmits the mating signal from plasma membrane into the nucleus through the G-protein coupled receptor and the mitogen-activated protein kinase (MAPK) cascade. According to current understanding of the mating pathway, we construct a system of ordinary differential equations to describe the process. Our model is consistent with a wide range of experiments, indicating that it captures some main characteristics of the signal transduction along the pathway. Investigation with the model reveals that the shuttling of the scaffold protein and the dephosphorylation of kinases involved in the MAPK cascade cooperate to regulate the response upon pheromone induction and to help preserve the fidelity of the mating signaling. We explored factors affecting the dose-response curves of this pathway and found that both negative feedback and concentrations of the proteins involved in the MAPK cascade play crucial roles. Contrary to some other MAPK systems where signaling sensitivity is being amplified successively along the cascade, here the mating signal is transmitted through the cascade in an almost linear fashion.     

Induction of sexual cell agglutinability of A mating type cells by alpha-factor in Saccharomyces cerevisiae.

Mating hormone, α-factor, which inhibits DNA synthesis and causes characteristic changes in cell morphology in $\text{a}$ mating type cells, was also responsible for induction of sexual cell agglutinability of $\text{a}$ mating type cells.     

Multiple signaling pathways regulate yeast cell death during the response to mating pheromones

Mating pheromones promote cellular differentiation and fusion of yeast cells with those of the opposite mating type. In the absence of a suitable partner, high concentrations of mating pheromones induced rapid cell death in approximately 25% of the population of clonal cultures independent of cell age. Rapid cell death required Fig1, a transmembrane protein homologous to PMP-22/EMP/MP20/Claudin proteins, but did not require its Ca2+ influx activity. Rapid cell death also required cell wall degradation, which was inhibited in some surviving cells by the activation of a negative feedback loop involving the MAP kinase Slt2/Mpk1. Mutants lacking Slt2/Mpk1 or its upstream regulators also underwent a second slower wave of cell death that was independent of Fig1 and dependent on much lower concentrations of pheromones. A third wave of cell death that was independent of Fig1 and Slt2/Mpk1 was observed in mutants and conditions that eliminate calcineurin signaling. All three waves of cell death appeared independent of the caspase-like protein Mca1 and lacked certain "hallmarks" of apoptosis. Though all three waves of cell death were preceded by accumulation of reactive oxygen species, mitochondrial respiration was only required for the slowest wave in calcineurin-deficient cells. These findings suggest that yeast cells can die by necrosis-like mechanisms during the response to mating pheromones if essential response pathways are lacking or if mating is attempted in the absence of a partner.