Subcellular distribution, chemical forms and physiological responses involved in cadmium tolerance and detoxification...

A pot experiment was conducted to investigate the detoxification mechanism of Agrocybe aegerita (A. aegerita). The physiological responses, subcellular distribution and chemical forms of cadmium (Cd) in A. aegerita grown in Cd stress were analyzed. The results showed that the biomass was decreased under Cd stress, while the production of malonaldehyde, thiols, and low-molecular-weight organic acids (LWMOAs) as well as the antioxidant enzymes in A. aegerita was increased compared with control group. The HPLC results showed that nine LWMOAs were found in A. aegerita with critic acid as the dominant and they played important role in the detoxification and accumulation of Cd in A. aegerita. More Cd was accumulated in pileus than in stipe. Differential centrifugation technique showed that the majority of Cd was compartmentalized in the soluble fraction (53-75%) and bound to the cell wall (19-42%). The proportion of Cd in the cell wall increased with the increase of the accumulation of Cd in the fruiting body, but in the soluble fraction showed an opposite trend. Furthermore, most of the Cd in A. aegerita was mainly in the forms of NaCl- (29-49%) and ethanol-extractable Cd (20-40%). The ethanol- and water-extractable Cd in stipe (60-66%) was higher than in pileus (43-49%). Thus intracellular detoxification mechanisms of Cd in A. aegerita is related to subcellular partitioning and chemical forms of Cd and well-coordinated physiological responses.