| In this paper,we studied the effects of artificial infection with pseudomonas fluorescens on the antioxidant index and non-specific immune index of grass carp serum,immune-related gene expression of grass carp,in order to provides a basis and reference valuable data understanding the mechanism of disease resistance prevention grass carp.1.We selected two strains of juveniles grass carp : a common group P of 180 juveniles grass carp with initial weight of(54.32±9.74)g and initial length of(13.92±1.68)cm,and another disease-resistant group K of 180 juveniles grass carp with initial weight of about(58.44±7.26)g and initial length of(14.86±2.07)cm.Each group were was randomly divided into three parallels,intraperitoneally injected 2x107 CFU/m L pseudomonas fluorescens bacteria liquid 0.1 ml/fish,and tagged in sequence of 0~21 d.The control group was recorded as group D.And we calculated the mortality during 21 d.The results showed that the cumulative mortality of the experimental group K was 4.5% lower than that of the group P,which indicated that the disease-resistant grass carp strain artificially infected with pseudomonas fluorescens had better resistance against the pathogtn.2.We took the same two strains of juveniles grass carp in 1 and infected them with and we collected serum separately at 0 d,1 d,3 d,7 d,14 d and 21 d.The control group was recorded as group 0,and the experimental groups,were marked as from 1 to 5 in turn.We analyzed the changes of serum antioxidant indexes,namely SOD,CAT,GSH-Px and MDA,and nonspecific immune indexes such as TP,ALT,AST,AKP,ACP,and LYZ in serum at different time points.The result showed that in group P,T-SOD increased firstly and then decreased(P<0.05);CAT,MDA,ALT,AST,AKP,ACP,and LYZ increased significantly(P<0.05);GSH-Px increased continuously(P<0.05),and A/G decreased firstly and then increased(P<0.05).In group K,except that ACP presented a sustainably increasing trend(P<0.05),which was different from that of group P,the overall trends of other indexes were basically consistent with those of group P.Compared with the control group,we found that the strains of grass carps in both experimental groups produced basic internal environment free radical adaptive repair after receiving artificial infection stimulation,and the change of CAT and ACP rate was the most significant in the two groups.The comprehensive comparison result showed that disease-resistant grass carps was more sensitive and faster to infection than common grass carps.3.We selected seven immune-related genes including TLR4,My D88,TRAF6,NEMO,NF-?B,IL-1? and IL-6,and analyzed the spatial and temporal expression of these genes in the skin,gill and intestinal tissues of two strains grass carp mfected with pseudomonas fluorescens,and the related toll-like receptor signaling pathway,NF-?B signaling pathway and the regulation of immune-related factors.The result showed that all the seven genes could be induced by intraperitoneal injection of pseudomonas fluorescens.In addition,the seven genes in both strains of grass carp could activate the expressions of two immune signaling pathways and their related downstream components.Moreover,IL-1? was most significantly expressed in the mucosal immune system of grass carp after it was infected with pseudomonas fluorescens. |
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