Transcriptome Analysis to Elucidate the Response of <i>Sanghuangporus baumii</i> (Pilát) L.W. Zhou &amp; Y.C. Dai to Sodium Treatment

To investigate the effects and underlying mechanisms of sodium (Na⁺) on the growth characteristics of <i>Sanghuangporus baumii</i> 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 <i>S. baumii</i> 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 <i>S. baumii</i> 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 <i>S. baumii</i> 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 <i>S. baumii</i>.