Study on growth and metabolites accumulation of Ganoderma lucidum mycelium by cadmium stress / 中草药

ABSTRACT

Objective: To study the effects of cadmium stress on mycelial growth and accumulation of metabolites in Ganoderma lucidum, and to explore the mechanisms affecting growth and accumulation of metabolites, and to provide evidence for controlling cadmium in the production and cultivation of G. lucidum. Methods: The mycelium of G. lucidum was cultured under the conditions of heavy metal ion cadmium concentration of 0, 0.5, 1, 4, 10, and 40 mg/L, and its biomass accumulation, intracellular ROS level, membrane oxidative damage, anti-oxidant enzyme activity, and ROS regulation related enzyme expression were analyzed. Results: When the concentration of cadmium reached 4 mg/L, the mycelial growth was inhibited. The levels of intracellular ROS, H2O2, and MDA increased significantly, increasing by 76%, 46% and 325%, respectively, and increased with the increase of cadmium concentration; The NADPH expression levels of oxidase gene (NOXA), superoxide dismutase gene (SOD1 and SOD4), and CATalase gene (CAT) were significantly up-regulated. When the cadmium concentration reached 10 mg/L, the inhibitory effect was significant. The colony growth diameter and the dry weight inhibition rate of fermentation mycelium were 26.15% and 32.78%, respectively. The total triterpenoid inhibition rate of G. lucidum was 33.7%, and the inhibition rate of total protein synthesis was 30.3%. Inhibition of polysaccharides was not significant. When the cadmium concentration reached 40 mg/L, the expression levels of Ascorbate peroxidase gene (APX) and Glutathione peroxidase gene (GPX) were significantly up-regulated. With the increase of cadmium concentration, the activities of SOD, CAT, APX, and GPX increased first and then decreased. When the concentration of cadmium reached 1 mg/L, the activity of GPX decreased and the activity of APX increased significantly. Exogenous addition of diphenyleneiodonium chloride (DPI), N-acetyl-L-cysteine (NAC) and vitamin C (VC) had significant effects on cadmium-induced G. lucidum clearance of ROS and reduction of MDA content. Conclusion: Cadmium stress causes the decrease of mycelial production and metabolite accumulation of G. lucidum, which may be due to the inhibition of GPX activity by cadmium ions, resulting in the accumulation of H2O2, causing the increase of ROS level and membrane oxidative damage, inhibiting mycelial growth and accumulation of metabolites, and regulating NOX. Up-regulation of gene expression results in an increase in anti-oxidant enzyme activity and expression to increase the clearance of reactive oxygen species. Therefore, the cadmium content should be controlled within the range of 1 mg/L during the production process.