Preliminary Study Of Pathway And Transcriptome Of Black Carp Infected With Aeromonas Hydrophila

Black carp(Mylopharyngodon piceus)is one of the “four family fishes” and it an important economic species for freshwater culture in China.Black carp is affected by many pathogenic microorganisms under natural conditions.Aeromonas hydrophila(AH)is the main pathogen causing bacterial sepsis in black carp.The mortality of black carp is extremely high,and it causes serious economic losses to the aquaculture of black carp.In this study,AH was labeled with GFP fluorescent protein to observe the path of infection of AH in the body of black carp.Differences in immune responses between diseaseresistant black carp and susceptible black carp had been explored by the transcription group.The MpMyD88 gene of the black carp had been identified and functionally analyzed based on the data of transcription group.The results obtained in this study were as follows:The recombinant plasmid(p-GFPuv-K)was transformed into AH and successfully expressed,which was similar to the half lethal concentration(LC50)and growth curve of the wild strain.The number of AH in the gill,liver,spleen,intestine,body kidney,head kidney,muscle,eye,brain,heart tissue and blood of the black carp within 72 hours after the marker infection was detected.The data indicate that the gill,intestines and injured skin of black carp were the main pathways for AH to enter the body.Blood is one of the mediators of AH in the body.Increasing the density of culture can increase the infection time of the bacteria.In the transcription group study,a total of 5243 genes was enriched in the GO(Gene ontology)analysis,and 323 related pathways was found in the KEGG(Kyoto Encyclopedia of Genes and Genome)analysis.A total of 1935 differentially expressed genes was found,mainly involved in cell adhesion,pathogen recognition,cellular immunity,cytokines,complement systems,and iron transport.The MpMyD88 gene was screened from the data of transcription group,and the fulllength of cDNA is 1658 bp and the open reading frame is 855 bp,encoding a protein of 284 amino acids.This protein had a conserved death domain and a typical TIR domain.MpMyD88 was found to be widely distributed in the tested tissues.After over expression or knockdown of MpMyD88,cytokines(TNF-?,IFN-?,IL-6,IL-8)also showed significant up or down-regulation.The antibacterial ability of cells over expression MpMyD88 was significantly stronger than that of the comparison group,while the knockdown group was significantly lower than the comparison group,and the over expression of MpMyD88 gene was found to significantly increase the activity of NF-?B.