| Heavy metal cadmium pollution has become an important issue affecting agricultural production safety and food safety in China.It is important to study the mechanism of crop tolerance to heavy metal cadmium and cultivate varieties resistant to heavy metal cadmium stress.In this study,the waxy corn inbred lines N46 and N28 were used as materials to analyze the transcriptome and metabolome data of seedling stage under cadmium stress,combined with their physiological and biochemical index analysis,to determine important stress response genes and metabolites.It provides a theoretical basis for the breeding of new waxy corn varieties,soil remediation and food safety.Physiological and biochemical parameters of the two inbred lines were measured,and the superoxide dismutase activity and catalase activity of the cadmium-sensitive inbred line N28 decreased by 9.7% and 10.8% at 24 hours of cadmium stress,and the superoxide dismutase activity and catalase activity of the cadmium-tolerant inbred line N46 increased by 3.5% and remained essentially unchanged at 24 hours of cadmium stress.However,N28 peroxidase activity also showed a decreasing trend after cadmium treatment,while N46 peroxidase activity showed an increasing trend after cadmium treatment.The glutathione reductase activity of N28 decreased by 21.2% after 24 h of cadmium treatment,in contrast to the 13.5% increase in glutathione reductase activity of the cadmium-tolerant material N46 after 24 h of cadmium treatment.Proline content increased by 10.7% in N28 and 22.4% in N46 after 24 h of cadmium treatment;malondialdehyde content increased in both cadmiumsensitive inbred line N28 and cadmium-tolerant inbred line N46 after cadmium stress,with N28 increasing by 15.2% and N46 increasing by 6.6%,and it is worth noting that malondialdehyde content in N28 was significantly higher than that in N46 before and after treatment.Analysis of gene transcription under cadmium stress in waxy maize inbred lines.At 4 hours of cadmium stress,1928 unique differential genes were produced by N46 and 3499 unique differential genes were produced by N28.N46 produced 2544 unique differential genes and N28 produced 510 unique differential genes at 24 hours of cadmium stress..The differentially expressed genes were annotated into GO and KEGG databases for functional annotation and enrichment analysis,and the results showed that the pathways with higher enrichment under N46 cadmium stress were oxidoreductase activity,antibiotic metabolic process,iron ion binding,and monooxygenase activity.The pathways with higher enrichment under N28 cadmium stress were response to organic cyclics,response to compounds with nitrogen.Metabolome analysis under cadmium stress in waxy maize inbred lines was performed using metabolome technology.Eighty-two differential metabolites were produced at 4 h of cadmium stress,of which 58 were unique to N46 and 24 to N28.Eighty-seven differential metabolites were produced at 24 h of cadmium stress,of which 66 were unique to N46 and 21 to N28.Annotating the metabolites in response to cadmium stress into the KEGG database,the pathways significantly enriched in N46 were flavonoid biosynthesis,aminoacyl-tRNA biosynthesis,ABC transporter,and biosynthesis of amino acids;the pathways significantly enriched in N28 were metabolic pathways and biosynthesis of secondary metabolites.A combined analysis of transcriptome data and metabolome data was performed.Pathway aminoacyl-tRNA biosynthesis appeared at two time points of cadmium stress in cadmium-tolerant material N46,but only at 4 h of cadmium-sensitive material N28.Zm00001d045375 was negatively correlated with metabolite L-methionine and Zm00001d012498 was positively correlated with metabolite L-methionine at both time points of cadmium-resistant material N46 treatment,while this gene and metabolite did not appear at 4 hours of N28 stress,and this pathway may have a great relationship with cadmium tolerance of N46.Pathway phenylpropanoid biosynthesis occurred at both time points of cadmium-sensitive material N28 treatment,but only at 24 hours of cadmium stress in cadmium-resistant material N46.It is speculated that this pathway may be greatly related to cadmium sensitivity of N28,and the genes and metabolites in these pathways need to be verified in the next experiments.Overall,there are significant differences in physiology,biochemistry,transcriptome and metabolic group between the two inbred lines after cadmium stress,and these findings are helpful to further understand the response mechanism of waxy maize under cadmium stress and improve the quality of waxy maize. |
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