Transcriptome Analysis Reveals Candidate Genes Involved in Light-Induced Primordium Differentiation in Pleurotus eryngii

Pleurotus eryngii, a highly valued edible fungus, is one of the major commercially cultivated mushrooms in China. The development of P. eryngii, especially during the stage of primordium differentiation, is easily affected by light. However, the molecular mechanism underlying the response of primordium differentiation to light remains unknown. In the present study, primordium expression profiles under blue-light stimulation, red-light stimulation, and exposure to darkness were compared using high-throughput sequencing. A total of 16,321 differentially expressed genes (DEGs) were identified from three comparisons. GO enrichment analysis showed that a large number of DEGs were related to light stimulation and amino acid biosynthesis. KEGG analyses demonstrated that the MAPK signaling pathway, oxidative phosphorylation pathway, and RNA transport were most active during primordium differentiation. Furthermore, it was predicted that the blue-light photoreceptor WC-1 and Deoxyribodipyrimidine photolyase PHR play important roles in the primordium differentiation of P. eryngii. Taken together, the results of this study provide a speculative mechanism that light induces primordium differentiation and a foundation for further research on fruiting body development in P. eryngii.

CHEMICALLY INDUCED MUTAGENESIS IN THE KING OYSTER MUSHROOM Pleurotus eryngii TO GENERATE HIGH-TEMPERATURE TOLERANT STRAIN

In this study, a high-temperature-tolerant strain of the king oyster mushroom (Pleurotus eryngii) was generated by chemical mutagenesis. Cultivation of P. eryngii generally involves incubating the mycelia at 25°C and then moving the spawns for further incubation at 18°C for fruitification. However, in tropical countries, the temperature is a major concern in the production of oyster mushroom where the average temperature is 32°C. In the current study, the mycelia were treated with ethyl methane sulphonate (EMS) or methyl methane sulphonate (MMS) for chemical-induced mutation. Seven mutants (EMS 1, 2, 6, 26, 35, 36, and 38) from EMS mutagenesis exhibited higher growth rates than the wild-type strain at 32°C. However, mutant strains from MMS mutagenesis showed a low growth rate when compared with wild-type. On sawdust substrate, the spawn running conditions for these strains were performed at 32°C, and fruitification occurred at 18°C. The yield and biological efficiency of EMS 36 and 38 mutants were higher than those of the wild-type strain. The activities of cellulase and xylanase of EMS 36 and 38 mutants showed that both these mutants had higher activities than the wild-type strain which may influence mushroom production. Therefore, these EMS 36 and 38 mutants can be cultivated in tropical countries, which could provide a high yield and reduce the cost during spawn running step.

Antimicrobial activity of the edible mushroom Pleurotus eryngii (DC.) Quél grown in liquid medium

Edible mushrooms have a number of medicinal properties and this study aimed to investigate the antimicrobial activity of Pleurotus eryngii DPUA1816 in metabolic broths after being grown in submerged cultivation. Mycelial fragments of pure P. eryngii culture was inoculated in sweet potato culture medium and incubated at 150 rpm for 15 days at 25°C. Pleurotus eryngii was also cultivated for 18 days under the same conditions, the mycelial biomass was separated by filtration for quantification. The supernatant was used in the diffusion test in agar and performed against Escherichia coli CCCD-E005, Staphylococcus aureus CCCD-S009, Pseudomonas aeruginosa CCCD-P004, Candida albicans CCCD-CC001, Candida parapsilosis CCCD-CC004 and Candida tropicalis CCCD-CC002. The samples showed no inhibitory activity against bacteria, however they showed some activity against C. albicans (12.17 mm), C. parapsilosis (27.67 mm) and C. tropicalis (13.67 mm). After being cultivated for 18 days, P. eryngii was able to inhibit all yeasts after 12 days of culture, with an inhibition halo of 29.33 mm at 16 days against C. parapsilosis. This study demonstrates the antifungal potential filtered liquids from P. eryngii cultivated in purple-skinned sweet potato culture medium, which suggests the possibility of the use of this species by the pharmaceutical industry as a natural source of biological action.

LIGNOCELLULOSE WASTE VALORIZATION BY AN ENZYMATIC COCKTAIL OF P. ERYNGII AND P. PULMONARIUS

The present study aimed to characterize Pleurotus eryngii and P. pulmonarius ligninolytic enzymes and to determine their potential for polymer degradation in common agroforestry residues. The peak of laccase activity (36052.33 U L-1) was observed after P. pulmonarius cultivation on oak sawdust. The maximal Mn-dependent peroxidase activity was reached by P. eryngii (2511.36 U L-1), while the highest level of versatile peroxidase activity was noted in P. pulmonarius (3053.03 U L-1), after fermentation of corn stalks. The highest level of lignin loss (46.28%) was achieved after cultivation of P. pulmonarius on corn stalks, but the most selective degradation of lignocellulose polymers was observed after P. eryngii cultivation on wheat straw. The obtained results lead to the conclusion that the studied P. eryngii and P. pulmonarius strains are good producers of ligninolytic enzymes and effective and selective depolymerizers of agroforestry residues, and therefore their use would be beneficial in numerous environmentally friendly technologies.

Transcriptomics Analysis of Primordium Formation in Pleurotus eryngii

Primordium formation is an important stage preceding the growth and development of the Pleurotus eryngii fruiting body. However, the molecular mechanisms underlying primordium formation remain unclear. In the present study, comparative transcriptomics was performed between mature mycelia and primordium to analyze the transcriptional properties during primordium formation in P. eryngii. A total of 19,655 differentially expressed genes (10,718 upregulated genes and 8937 downregulated genes) were identified. These differentially expressed genes were involved in cell wall degradation, carbohydrate hydrolysis, light perception, and cAMP signal transduction. These results aid further understanding of the transcriptional changes and the molecular processes underlying primordium formation and differentiation, which may lay the foundation for improving the cultivation and quality control of P. eryngii.