The Importance Of Nitric Oxide As The Molecular Basis Of Molecular Hydrogen Fumigation-induced Alleviation Of Cadmium Stress On Ganoderma Lucidum

Ganoderma lucidum is among the most important medicinal basidiomycetes because it can produce many compounds with pharmacological activity.In general,the growth and development of Ganoderma lucidum are often affected by cadmium stress,which leads to excess cadmium（Cd）accumulation and consequently less growth rate and productivity.Therefore,the establishment of a green and pollution-free practice method to enhance cadmium tolerance of Ganoderma lucidum has been the focus of research.Hydrogen gas（H₂）,as a colorless,odorless,and non-toxic gas,has been proved to be a bioactive molecule in many experiments in Animals,Plants and few edible fungi studies.Hydrogen,like nitric oxide,could be used as a new gas signal molecule to regulate a variety of physiological responses of Ganoderma lucidum,including improving cadmium tolerance.However,the relevant molecular mechanism is still unclear.In addition,spraying with hydrogen-rich water is also difficult to be widely used as a cultivation condition of Ganoderma lucidum.Therefore,the molecular mechanism of the hydrogen alleviating effect on the cadmium-caused inhibition of Ganoderma lucidum growth was studied by means of the hydrogen fumigation method and its effects on pharmacological and molecular biology aspects were reported.Specific test contents are as follows:1.50%saturation of hydrogen-rich water and 3%（volume）of H₂ fumigation could significantly alleviate cadmium-caused inhibition of Ganoderma lucidum mycelial growth,characterized by larger growth diameter,and biomass dry weight,stronger antioxidant capacity and less Cd uptake than treatments with no H₂ fumigation.And the 3%H₂ fumigation alleviation effect was significantly higher than the 50%saturation of hydrogen-rich water.2.The inhibitory effect of cadmium stress on the growth of Ganoderma lucidum was accompanied by an increase in the NO content,and H₂ fumigation treatment could significantly enhance NO content under cadmium stress.However,the Nitrate reductase inhibitor,sodium tungstate1zsx and the NO scavenger,cPTIO could reverse the H₂ gas fumigation-induced NO content and the biological effects of H₂,suggesting that nitrate reductase mediated NO may be involved in the hydrogen-induced alleviation of the cadmium stress-caused inhibition of the Ganoderma lucidum mycelial growth.3.The detection results of antioxidant capacity,proline and cadmium content under H₂fumigation,cPTIO,and sodium tungstate separately and in combination showed that H₂alleviated the inhibition of Cd on the growth diameter and dry weight of mycelia,decreased the accumulation of Cd,promoted the increase of proline,decreased the content of reactive oxygen species（ROS）,decreased the content of TBARS,promoted the activity of antioxidant enzymes and gene expression,which were all reversed by cPTIO or sodium tungstate treatment,further suggesting the mediated effect of NO signal.These results indicate that nitrate reductase-dependent NO is involved in the hydrogen fumigation-induced alleviation of Cd stress on Ganoderma lucidum by improving the antioxidant capacity of Ganoderma lucidum and reducing cadmium absorption.The results not only provided a more convenient way for H₂ treatment of Ganoderma lucidum under cadmium stress but also elucidated the molecular mechanism of the H₂–induced alleviation of cadmium stress on the growth inhibition of Ganoderma lucidum,which provided a new theoretical basis for the application of hydrogen in Ganoderma lucidum production.