Transcriptome Analysis to Elucidate the Response of Sanghuangporus baumii (Pilát) L.W. Zhou & Y.C. Dai to Sodium Treatment

Abstract

To investigate the effects and underlying mechanisms of sodium (Na⁺) on the growth characteristics of Sanghuangporus baumii mycelia, a single-factor Na⁺ addition experiment was performed. We found that treatment with 10 mmol/L Na⁺ (Na10) significantly increased the growth rate (0.41 ± 0.01 cm/d) and biomass (4.27 ± 0.05 g/L) of S. baumii mycelia, surpassing the control (Ck) group by 3.14% and 4.06%, respectively. In contrast, treatment with 100 mmol/L Na⁺ (Na100) resulted in a significant reduction in growth rate (0.34 ± 0.01 cm/d) and biomass (3.25 ± 0.02 g/L) of S. baumii mycelia compared to the Ck group. Transcriptome analysis further revealed that low Na⁺ concentrations (10 mmol/L) promoted the accumulation of soluble sugars (7.63 ± 0.54 mg/g) and upregulated the expression of pertinent genes, thereby accelerating mycelial growth. On the other hand, high Na⁺ concentrations (100 mmol/L) led to H₂O₂ accumulation (12.18 ± 0.24 μmol/g), causing toxicity in S. baumii mycelia. High Na⁺ concentrations also significantly boosted the production of valuable metabolites, such as triterpenoids (19.65 ± 0.22 mg/g), although the exact mechanisms remain to be elucidated. Overall, we suggest an effective approach for accelerating mycelial growth cycles and enhancing the production of high-value bioactive compounds from S. baumii.

Keywords: Sanghuangporus baumii; peroxisome pathway; sodium; starch and sucrose metabolism; triterpenoids.

Figure 1.

Growth characteristics of Sanghuangporus baumii mycelia under Na⁺ treatment (the mean difference being significant at the 0.05 level, p < 0.05). (A) Colony morphology. (B) Growth rate. (C) Biomass.

Figure 2.

Transcriptome analysis of growth differences in Sanghuangporus baumii mycelia under Na⁺ treatment (the mean difference being significant at the 0.05 level, p < 0.05). (A) RNA gel electrophoresis. (B) PCA score plot of transcript profiles (Ck, Na10, and Na100 groups). (C) Volcano plot of up- and downregulated DEGs from pairwise comparisons. (D) qRT-RCR validation of gene expression. (E) KEGG pathway enrichment analysis.

Figure 3.

Soluble sugar content and gene expression levels in Sanghuangporus baumii under Na⁺ treatment (the mean difference being significant at the 0.05 level, p < 0.05). (A) Expression levels of soluble sugar-related genes. (B) Soluble sugar content.

Figure 4.

Antioxidant system alterations in Sanghuangporus baumii under Na⁺ treatment (the mean difference being significant at the 0.05 level, p < 0.05). (A) Gene expression levels. (B) SOD, (C) CAT, and (D) POD activities. (E) H₂O₂ content.

Figure 5.

Total triterpenoid content and gene expression levels in Sanghuangporus baumii under Na⁺ treatment (the mean difference being significant at the 0.05 level, p < 0.05). (A) Triterpenoid-related gene expression levels. (B) Total triterpenoid content.