Identification and functional analysis of pheromone and receptor genes in the B3 mating locus of Pleurotus eryngii.

Pleurotus eryngii has recently become a major cultivated mushroom; it uses tetrapolar heterothallism as a part of its reproductive process. Sexual development progresses only when the A and B mating types are compatible. Such mating incompatibility occasionally limits the efficiency of breeding programs in which crossing within loci-shared strains or backcrossing strategies are employed. Therefore, understanding the mating system in edible mushroom fungi will help provide a short cut in the development of new strains. We isolated and identified pheromone and receptor genes in the B3 locus of P. eryngii and performed a functional analysis of the genes in the mating process by transformation. A genomic DNA library was constructed to map the entire mating-type locus. The B3 locus was found to contain four pheromone precursor genes and four receptor genes. Remarkably, receptor PESTE3.3.1 has just 34 amino acid residues in its C-terminal cytoplasmic region; therefore, it seems likely to be a receptor-like gene. Real-time quantitative RT-PCR (real-time qRT-PCR) revealed that most pheromone and receptor genes showed significantly higher expression in monokaryotic cells than dikaryotic cells. The pheromone genes PEphb3.1 and PEphb3.3 and the receptor gene PESTE3.3.1 were transformed into P5 (A3B4). The transformants were mated with a tester strain (A4B4), and the progeny showed clamp connections and a normal fruiting body, which indicates the proposed role of these genes in mating and fruiting processes. This result also confirms that PESTE3.3.1 is a receptor gene. In this study, we identified pheromone and receptor genes in the B3 locus of P. eryngii and found that some of those genes appear to play a role in the mating and fruiting processes. These results might help elucidate the mechanism of fruiting differentiation and improve breeding efficiency.

Vegetative Growth of Four Strains of Hericium erinaceus Collected from Different Habitats.

Vegetative growth of four different strains of Hericium erinaceus was observed. The temperature suitable for optimal mycelial growth was determined to be 25℃, with growth observed in the extend temperature range of 20~30℃. The different strains of this mushroom showed distinct pH requirements for their optimum vegetative growth, with the most favorable growth observed at pH 6. Considering vegetative mycelial growth, PDA, YM, Hennerberg, Hamada, and Glucose peptone were the most favorable media, and Czapek Dox, Hoppkins, Glucose tryptone, and Lilly were the most unfavorable media for these mushroom strains. With the exception of lactose, most of the carbon sources assayed demonstrated favorable vegetative growth of H. erinaceus. For mycelial growth, the most suitable nitrogen source was alanine and the most unsuitable was histidine. Oak sawdust medium supplemented with 10~20% rice bran was the best for mycelial growth of the mushroom.

Physicochemical Requirement for the Vegetative Growth of Schizophyllum commune Collected from Different Ecological Origins.

Schizophyllum commune is an edible and medicinal mushroom widely distributed in the world. The optimal growth conditions for the mycelia of 10 strains of the fungus were investigated. The temperature suitable for the mycelial growth and density was obtained at 30~35℃. Among the tested conditions, the minimum mycelial growth was found at 15℃. In case of pH, the most favorable growth was found at pH 5. The results indicated that this mushroom well adapted to high temperature and low pH for its mycelial growth. Considering growth phenotype of mycelia, Hamada, Hennerberg, PDA and YM were the most suitable and Lilly, Glucose triptone, Glucose peptone and Hoppkins were the most unfavorable among tested media for the mycelial growth of S. commune. Out of tested carbon sources, dextrin and fructose were the most suitable and lactose, mannose and sorbitol were the unsuitable for the fungus. Compact mycelial density was obtained from most of the carbon sources. Among used nitrogen sources, calcium nitrate, potassium nitrate and alanine were the most appropriate and the most incompatible were ammonium phosphate, histidine, urea and arginine for mycelial growth of S. commune on the culture media. Calcium nitrate, histidine and potassium nitrate showed moderately thin or thin, and rest of nitrogen sources showed compact or moderately compact mycelial density.

Genes Expressed During Fruiting Body Formation of Agrocybe cylindracea.

Agrocybe cylindracea, an edible mushroom belonging to Bolbitiaceae, Agaricales, is widely used as invaluable medicinal material in the oriental countries. This study was initiated to find the genes expressed during the fruiting body formation of A. cylindracea. The cDNAs expressed differentially during fruiting body morphogenesis of A. cylindracea were isolated through subtractive hybridization between vegetative mycelia and fruiting bodies. The cDNAs expressed in the fruiting body morphogenesis of A. cylindracea were cloned and twenty genes were identified. Eleven were homologous to genes of known functions, three were homologous to genes in other organism without any function known. Six were completely novel genes specific to A. cylindracea so far examined. Some genes with known functions were a pleurotolysin, a self-assembling poreforming cytolysins; Aa-Pri1 and Pir2p, specifically induced genes during fruiting initiation of other mushroom, Agrocybe aegerita; an amino acid permease; a cytochrome P450; a MADS-box gene; a peptidylprolyl isomerase; and a serine proteinase. For other clones, no clear function was annotated so far. We believe the first report of the differentially expressed genes in fruiting process of A. cylindracea will be great helps for further research.