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 (H2) can reduce cadmium (Cd) toxicity inGanoderma lucidumhas remained largely unknown. Here, we report that Cd-induced growth inhibition inG. lucidumwas significantly alleviated by H2fumigation or hydrogen-rich water (HRW), evaluated by lower oxidative damage and Cd accumulation. Moreover, the amelioration effects of H2fumigation were better than of HRW in an optimum concentration of H2under our experimental conditions. Further results showed that H2-alleviated growth inhibition inG. lucidumwas 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 H2-induced NR activity with sodium tungstate. The role of NO in H2-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 H2-alleviated Cd toxicity inG. lucidumthrough rebuilding redox homeostasis, increasing cysteine and proline levels, and reducing Cd accumulation. These findings may open a new window for H2application in Cd-stressed economically important fungi.Keywords:hydrogen fumigation;nitric oxide;hydrogen-rich water;stress alleviation;cysteine;proline;Ganoderma lucidum