Study On The Immune Response Involved In The Resistance Of Triploid Crucian Carp To Cadmium Stress

The pollution of cadmium?Cd?to the water body seriously threatened the healthy growth of fish,and the previous study of our group found that oxidative stress is one of the important regulatory mechanisms of triploid crucian carp?3n?resistance to Cd stress.In order to further analyze the other possible mechanisms of 3n against Cd stress,this study through the analysis of liver function and the detection of immune-related indicators,molecular biological analysis based on transcriptomics technology,and combined the comparative study of 3n and diploid crucian carp?2n?to explore whether 3n participates in body regulation under Cd exposure conditions through immune response.The main results are as follows:1.The normal structure of liver tissue is an important guarantee for its functioning.The results showed that after exposure to Cd,the levels of T-Bil,AST and ALT in serum and the MDA content in liver were significantly increased in 2n,but these indicators did not change significantly in 3n,which suggested that Cd exposure damaged liver tissue of 2n and caused liver function impairment.2.Cd exposure resulted in a significant decrease in the levels of TP,ALB and GLB,a significant increase in ADA,while ALP did not change significantly in serum of 2n.Cd exposure significantly reduced ADA in serum of 3n,but no significant changes were found in TP,ALB,GLB and ALP.Cd exposure significantly inhibited the serum LZM activity level of2n,while the level of serum LZM activity of 3n was slightly increased.Cd exposure significantly inhibited the level of ASOR activity of 2n,but there was no significant effect on the ASOR activity level of 3n.The resules indicatd that Cd stress inhibited the immune response of 2n and caused damage or even death of 2n,but induced the immune response of3n to protect its body health status,reflecting the stronger immunity of3n.3.Understanding the response of 3n immune response to Cd stress at the genetic level based on transcriptomics technology.Preliminary manual screening and analysis of the transcriptome data of the liver of 3n before and after Cd treatment showed that Cd exposure caused 658immune-related genes differentially expressed?/log₂FC/>1 and p-value<0.05?,301 of them were up-regulated and 357 were down-regulated.Further analysis of the significance of these immune-related differentially expressed genes?DEGs??/log₂FC/?1.5 and p-value<0.05?revealed that 437 immune-related DEGs were significant,of which 224 were significantly up-regulated and 213 were significantly down-regulated.KEGG classification analysis revealed that these 658immune-related DEGs were annotated to a total of 32 immune-related pathways,of which the MAPK signaling pathway was the most significantly enriched.GO classification analysis found that these DEGs were mainly involved in the biological processes such as immune response,inflammatory response and apoptosis process.4.Based on qRT-PCR technology,the transcriptome of 3n was verified and the expression of 10 important immune-related genes were detected in the liver of 2n and 3n before and after Cd exposure.The results showed that the expression of il1?in 2n and 3n was significantly up-regulated,but the increase in 3n was more significant.The expression of il6,tnfsf12,tnfrsf13?,ccl4,cox2,tlr4,hsp70,jun,fos were all down-regulated in different degrees in 2n,but up-regulated in different degrees in 3n after Cd exposure.The resules further supported the above biochemical results from the molecular level.In addition,the changes of these immune related genes in the transcriptome were basically consistent with the results of qRT-PCR,indicating the reliability of the transcriptome.This study showed that the immune response played a positive role in the resistance of 3n to Cd stress and was one of the important regulatory mechanisms of 3n against Cd stress.Our results further enrich the theoretical basis of fish resistance to heavy metal stress,and provide a theoretical reference for the selection and cultivation of excellent fish species,healthy fish breeding and ecological restoration of water pollution.