Interdependent nitric oxide and hydrogen peroxide independently regulate the coix seed oil-induced triterpene acid accumulation in Ganoderma lingzhi.

Recent progress has been made in adding exogenous vegetable oils in culture media to promote bioactive metabolite production in several medicinal mushrooms, but the mechanism is still unclear. In this study, we found that the vegetable oil coix seed oil (CSO) could induce the biosynthesis of triterpene acids (TAs) and also significantly increase cytoplasmic nitric oxide (NO) and hydrogen peroxide (H2O2) concentrations in the mycelium of Ganoderma lingzhi. The change in TA biosynthesis caused by CSO could be reversed by adding NO scavenger or H2O2 scavenger, and adding NO scavenger or H2O2 scavenger resulted in the reduction of the cytoplasmic H2O2 or NO concentration under CSO treatment, respectively. Moreover, adding NO scavenger or H2O2 scavenger reversed TA biosynthesis, which could be rescued by H2O2 or NO donor, respectively. Taken together, our study indicated that both NO and H2O2 were involved in the regulation of TA biosynthesis, and CSO-activated NO and H2O2 were interdependent but independently regulated the TA biosynthesis under CSO treatment in G. lingzhi.

Identification of Reference Genes and Analysis of Heat Shock Protein Gene Expression in Lingzhi or Reishi Medicinal Mushroom, Ganoderma lucidum, after Exposure to Heat Stress.

Ganoderma lucidum has been considered an emerging model species for studying how environmental factors regulate the growth, development, and secondary metabolism of Basidiomycetes. Heat stress, which is one of the most important environmental abiotic stresses, seriously affects the growth, development, and yield of microorganisms. Understanding the response to heat stress has gradually become a hotspot in microorganism research. But suitable reference genes for expression analysis under heat stress have not been reported in G. lucidum. In this study, we systematically identified 11 candidate reference genes that were measured using reverse transcriptase quantitative polymerase chain reaction, and the gene expression stability was analyzed under heat stress conditions using geNorm and NormFinder. The results show that 5 reference genes-CYP and TIF, followed by UCE2, ACTIN, and UBQ1-are the most stable genes under our experimental conditions. Moreover, the relative expression levels of 3 heat stress response genes (hsp17.4, hsp70, and hsp90) were analyzed under heat stress conditions with different normalization strategies. The results show that use of a gene with unstable expression (SAND) as the reference gene leads to biased data and misinterpretations of the target gene expression level under heat stress.