Sanghuangporus baumii (Pil at) L.W. Zhou & Y.C. Dai, a popular medicinal fungus, has been used to treat several diseases by its triterpenoids bioactive ingredient for many years. However, the triterpenoids content of S. baumii is low and their biosynthesis mechanisms are not clearly understood. In order to reveal the regulation mechanism of triterpenoids biosynthesis in S. baumii, the cDNA encoding isopentenyl diphosphate isomerase (IDI) involved in triterpenoids biosynthesis was cloned and named as SbIDI (GenBank number MK955885). The open reading frame of the SbIDI gene cDNA comprised 792 bp and encoded a polypeptide of 263 amino acids with a predicted protein molecular weight of 29.80 kDa. The transcript level of the SbIDI gene and triterpenoids content of S. baumii were detected at different developmental stages. The results showed that the transcript level of the SbIDI gene and triterpenoids content had almost the same trend of change, increased first and then decreased dynamically. The highest transcript level of the SbIDI gene occurred earlier than the highest triterpenoids content, indicating that the SbIDI gene may play an important role in triterpenoids biosynthesis in S. baumii. Moreover, the SbIDI gene cDNA was successfully expressed in Escherichia coli BL21 (DE3), and the protein bands were consistent with the prediction.The results will lay a foundation for further study of the function of the SbIDI gene.

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Triterpenoids are secondary metabolites produced by the fungus Sanghuangporus baumii that have important pharmacological activities. However, the yield of triterpenoids is low and cannot meet market demand. Here, we treated S. baumii with several concentrations of MeJA (methyl jasmonate) and found that the total triterpenoid content was highest (23.31 mg/g) when the MeJA concentration was 250 μmol/L. qRT-PCR was used to quantify the transcription of five key genes involved in triterpenoid biosynthesis. The results showed that the relative transcription of most genes increased with increasing MeJA concentration, indicating that MeJA is a potent inducer of triterpenoid biosynthesis in S. baumii. To further explore whether other terpenoid biosynthesis pathways are also involved in the accumulation of triterpenoids induced by MeJA, we measured the contents of cis-Zeatin (cZ), gibberellins (GAs), and the transcript levels of related biosynthesis genes. We found that MeJA significantly inhibited the biosynthesis of cZ, GAs, and the transcription of related genes. The repressive effects of MeJA on cZ and GA accumulation were further confirmed by growth rate and biomass assays. In conclusion, our study provides an effective method to enhance the triterpenoid content of S. baumii, and also provides novel insights into the mechanism of MeJA-induced triterpenoid biosynthesis.

The present study reports the isolation and analysis of a beta-glucosidase gene (accession number MN816859) from the fungus Auricularia heimuer. The Aa-bgl gene comprises 2583 bp and encodes a putative polypeptide of 860 amino acids. BlastP analysis revealed conserved glycoside hydrolase family 3 domains. Recombinant plasmid pET-32a-bgl was constructed to overexpress the target protein in Escherichia coli BL21, and sodium dodecyl sulphate polyacrylamide gel electrophoresis analysis revealed target bands between 100 kDa and 135 kDa, consistent with the expected molecular weight. Additionally, the transcription levels of Aa-bgl at different developmental stages were investigated, and the results showed that the expression levels increased with the maturation of the fruiting bodies. In mature fruiting bodies, the levels were 6.69-fold higher than in controls (mycelium at 6 days). We therefore speculate that Aa-bgl may be correlated with development in A. heimuer. The findings provide a theoretical basis for studying the function of this beta-glucosidase in future work.