Differential Expression Of Immune-related Genes In The Skin And Gills Of Carassius Auratus Infected With Aeromonas Hydrophila

Teleost fish skin and gills mucosa-associated lymphoid tissue were the primary invasion sites of pathogenic microorganisms and played important roles in the immune responses.In this study,we established a model that carp(Carassius auratus)infected with Aeromonas hydrophila.The induced skin and gills samples were RNA-sequenced by Illumina Hiseq 2000 platform.A total of 118111 unigenes were assembled from 13290171480 nt filtered reads in skin,while 104213 unigenes were assembled from 9776335500 nt filtered reads in gills.The mean length and N50 size of assembled skin transcripts were 958 nt and 1846 nt,while the gills were 928 nt and1798nt.There were 94776 and 84259 unigenes annotated by blast searches against the NCBI non-redundant protein database in skin and gills,respectively.GO and KEGG pathways statistic analysis showed the differentially expressed genes(DEGs)involved in antigen processing and presentation,phagosome,cell adhesion molecules,chemokines,cell cycle,complement and coagulation systems,natural killer cell mediated cytotoxicity,apoptosis and TLR,NF-κB,BCR,TCR,NLR,JAK-STAT,MAPK,TGF-β,p53,Wnt,VEGF,Notch,mTOR signaling pathways in skin and gills mucosal immune response process.In order to study the immune mechanisms of mucosal system,real-time quantitative PCR(qRT-PCR)was used to verify the screened immune related DEGs’ expressed level with specific primers.As a result,11 DEGs were demonstrated in carp skin,among which the major histocompatibility complex(MHC-Ι,MHC-II),complement protein(C7)and C-reactive protein(CRP-2)showed high expression(fold change >5).Moreover,the expression of MHCΙ,CRP-2,nuclear transcription factor inhibitor protein(IkB α),tumor necrosis factor(TNF β),interferon-stimulated genes(RSAD2),tumor necrosis factor receptor-associated factor(TRAF6)at T1(infected 6h)were higher than T2(infected 12h);MHC-II,C7,interleukin(IL-22),interferon-induced GTP-binding protein(Mx1)expressed higher than infected 12 h.The skin qRT-PCR recults were close to the RNA-seq results.12 DEGs from gills were identified and the expression level of MHC-I and interleukin(IL-17C)were high(fold change >5).The gills qRT-PCR results were close to or even higher than RNA-seq results.This is the first study of Aeromonas hydrophila infected C.auratus skin and gills,the analysis on the transcriptional level would help to understand the defense mechanisms of fish skin and gills mucosal immune response to bacteria.