The Importance of Nitric Oxide as the Molecular Basis of the Hydrogen Gas Fumigation-Induced Alleviation of Cd Stress on Ganoderma lucidum

Whether or not hydrogen gas (H-2) can reduce cadmium (Cd) toxicity in Ganoderma lucidum has remained largely unknown. Here, we report that Cd-induced growth inhibition in G. lucidum was significantly alleviated by H-2 fumigation or hydrogen-rich water (HRW), evaluated by lower oxidative damage and Cd accumulation. Moreover, the amelioration effects of H-2 fumigation were better than of HRW in an optimum concentration of H-2 under our experimental conditions. Further results showed that H-2-alleviated growth inhibition in G. lucidum was accompanied by increased nitric oxide (NO) level and nitrate reductase (NR) activity under Cd stress. On the other hand, the mitigation effects were reversed after removing endogenous NO with its scavenger cPTIO or inhibiting H-2-induced NR activity with sodium tungstate. The role of NO in H-2-alleviated growth inhibition under Cd stress was proved to be achieved through a restoration of redox balance, an increase in cysteine and proline contents, and a reduction in Cd accumulation. In summary, these results clearly revealed that NR-dependent NO might be involved in the H-2-alleviated Cd toxicity in G. lucidum through rebuilding redox homeostasis, increasing cysteine and proline levels, and reducing Cd accumulation. These findings may open a new window for H-2 application in Cd-stressed economically important fungi.