Characterization Of Cadmium Accumulation And Response Mechanisms To Cadmium Stress In Cunninghamia Lanceolata

Increasing soil cadmium pollution has become more and more serious.Cunninghamia lanceolata,as a fast-growing,high-yielding and resistant southern dominant tree species.Understanding Cd absorption,translocation,and detoxification mechanisms in C.lanceolata could help us develop phytoremediation of cadmium-contaminated soils.In this study,five treatments were established:no Cd addition,25 mg·kg^-1 Cd addition,50 mg·kg^-1 Cd addition,75 mg·kg^-1 Cd addition;and 100 mg·kg^-1 Cd addition.The growth morphology,physiology,and biochemistry,Cd content in various tissues and subcellular fractions,and transcriptome sequencing were determined to study Cd uptake,transport,and detoxification mechanisms in C.lanceolata,as well as their tolerance mechanisms.The results showed that:（1）Low Cd concentrations can promote the growth of C.lanceolata.However,C.lanceolatar was subjected to toxic effects under high Cd stress.Cd inhibited the growth of C.lanceolata.In terms of growth morphology,cadmium treatment at 50 mg·kg^-1 significantly increased the growth rate of C.lanceolata height and total root length of the root system,while cadmium treatment at 100 mg·kg^-1significantly inhibited the growth rate of C.lanceolata ground diameter,leaf biomass,total biomass and root tip number.（2）At the physiological level,a significant increase in MDA content in C.lanceolata leaves and roots at a concentration of 100 mg·kg^-1 Cd led to an increase in membrane lipidation and oxidation.A protective enzyme system exists in C.lanceolata,and with increasing Cd concentration,Both SOD and POD changed significantly when subjected to Cd stress,maintaining a high level of resistance to Cd stress through regulation of the antioxidant system.（3）At the tissue level,the accumulation of Cd in C.lanceolata was mainly concentrated in the root system,and Cd accumulation in each tissue was root>stem>leaf.The pattern of distribution of Cd in each tissue of C.lanceolata at the subcellular level was cell wall>soluble>organelle.The cadmium content of each subcellular fraction increased significantly with increasing cadmium concentration,which is the important way of mitigating cadmium damage to the plant through compartmentalisation.（4）At the molecular level,significant differences in gene expression of multiple pathways occurred in cedar under cadmium stress.The key enzymes associated with the differentially gene-enriched pathways were significantly up-or down-regulated,mitigating the toxic effects on cedar by regulating metabolites in metabolic pathways such as gluconeogenesis,amino acid metabolism lipid metabolism,which in turn altered metabolic processes such as amino acid metabolism and glutathione metabolism through gene regulation of gluconeogenesis,redox metabolism,photosynthesis and glutathione metabolism.The results showed that cadmium tolerance in C.lanceolata may be related to the differential expression of relevant response genes and the physiological response to the response regulated by the genes,and is ultimately reflected in differences in plant morphogenesis and growth and development.C.lanceolata may reduce the toxic effects of Cd by maintaining cellular morphology and balancing oxidative stress by regulating the content of metabolites in metabolic pathways such as sugar metabolism,amino acid metabolism and lipid metabolism,and thus altering metabolic processes such as amino acid metabolism and glutathione metabolism.