Mating biology in Peniophora cinerea (Basidiomycetes)

Mating tests were performed to analyze the genetic relationship between two intersterile sibling species in Peniophora cinerea (Fr.) Cooke in Europe. Two newly collected specimens from North Europe were found to be compatible with both sibling species, which strongly suggests a close genetic relationship and a sterility barrier of simple genetic origin. The two sibling species, which differ in their substrate selectivity, are accepted as subspecies. One subspecies is restricted to decorticated wood of Fagus, and occasionally the fruit bodies are associated with insect galls. Intersterility was also found in some combinations with two other specimens from Canada and Turkey, but no linkage was found with a particular substrate. Specimens from Taiwan were found to be partially compatible with specimens from Europe, Turkey, and Canada. Distinct differences between the subspecies were found in banding patterns from isoelectric focusing of buffer-soluble mycelial proteins. It is proposed that the kind of intersterility found here is intraspecific and should be looked upon as part of a propagation strategy. Key words: speciation, evolution, Basidiomycetes, isoelectric focusing, insect gall, mating test.

Improved media for testing the mating reaction and genetic complementation of Ustilago hordei

The sexual cycle of Ustilago hordei, which results in the formation of teliospores, requires growth on its barley host for completion. However, the early steps of mating, including conjugation and the formation of dikaryotic mycelium, can occur on artificial media. The addition of activated charcoal to a variety of media enhanced the stability and intensity of the mating reaction as measured by mycelium formation. The incubation time at which the strongest mating reaction occurred was also reduced. The dikaryotic nature of the mycelia that resulted from mating on charcoal-containing media was confirmed by fluorescence microscopy. Complementation assays using minimal medium containing activated charcoal demonstrated allelism of mutations in auxotrophic sporidial strains of opposite mating type. The ease and reliability of this mating test allow for rapid identification of the mating type of unknown isolates and progeny of crosses, as well as providing a dependable procedure for performing complementation tests. Key words: barley, covered smut, Hordeum vulgare, mating type.

Mutants of Saccharomyces cerevisiae unresponsive to cell division control by polypeptide mating hormone.

Temperature-sensitive mutations that produce insensitivity to division arrest by alpha-factor, a mating pheromone, were isolated in an MATa strain of Saccharomyces cerevisiae and shown by complementation studies to difine eight genes. All of these mutations (designated ste) produce sterility at the restrictive temperature in MATa cells, and mutations in seven of the genes produce sterility in MAT alpha cells. In no case was the sterility associated with these mutations coorectible by including wild-type cells of the same mating type in the mating test nor did nay of the mutants inhibit mating of the wild-type cells; the defect appears to be intrinsic to the cell for mutations in each of the genes. Apparently, none of the mutants is defective exclusively in division arrest by alpha-factor, as the sterility of none is suppressed by a temperature-sensitive cdc 28 mutation (the latter imposes division arrest at the correct cell cycle stage for mating). The mutants were examined for features that are inducible in MATa cells by alpha-factor (agglutinin synthesis as well as division arrest) and for the characteristics that constitutively distinguish MATa from MAT alpha cells (a-factor production, alpha-factor destruction). ste2 Mutants are defective specifically in the two inducible properties, whereas ste4, 5, 7, 8, 9, 11, and 12 mutants are defective, to varying degrees, in constitutive as well as inducible aspects. Mutations in ste8 and 9 assume a polar budding pattern unlike either MATa or MAT alpha cells but characteristic of MATa/alpha cells. This study defines seven genes that function in two cell types (MATa and alpha) to control the differentiation of cell type and one gene, ste2, that functions exclusively in MATa cells to mediate responsiveness to polypeptide hormone.