Effects Of Vibrio Parahaemolyticus And Aflatoxin B1 On Hepatopancreas Of Litopenaeus Vannamei

The effects of Vibrio parahaemolyticus and AFB1 on hepatopancreas of Litopenaeus vannamei were studied from the biochemical and molecular levels.In order to determine the impact of pathogenic Vibrio parahaemolyticus(Vp)on the hepatopancreas of Litopenaeus vannamei,shrimps with weights of(2.2±0.24)g were challenged with Vp of concentrations of 5×107 CFU/m L for 36 hours.The tissues of hepatopancreas from experimental and control group were collected at the 6th,12 th,24th and 36 th hour of the experiment,to evaluate antioxidant enzyme activities,immune and m TOR signal pathway related gene expression levels.The results showed that after challenged with Vp,SOD activity was significantly higher than that of control group(P<0.05),while CAT,GSH-PX and GST activities all increased at first and decreased subsequently,reaching peak value at 12 h,6 h and 24 h respectively(P<0.05).The relative expression levels of Rab and Grim-19 were significantly higher than that of control group(P<0.05),crustin and Pro PO were up-regulated at first and decreased after reaching their peaks at 12 h and 24 h respectively,while the level of GST gene was significantly lower than that of control group during 12-36 h(P<0.05),these results showed that the functions of immune system were affected by Vp.Several important genes in m TOR signal pathway were also been qualified by q RT-PCR.The relative expression levels of 4EBP gene was significantly higher than that of control group(P<0.05).e IF4E1 A,e IF4E2 were both up-regulated at first and decreased after reaching peak value at 12 h and 6 h respectively(P<0.05).The level of P70s6 k was significantly lower than that of control group after challenged(P<0.05).The results indicated that Vp challenge had noticeable impact on antioxidant enzyme activities,immune and m TOR signal pathway related gene expression of Litopanaeus vannamei,and significant destructive effect to the shrimp's immune system.To investigate the effects of aflatoxin B1(AFB1)on the antioxidant enzyme activities,histopathology and transcriptome in Litopenaeus vannamei,300 shrimps were randomly divided into two groups and fed two diets containing 0 and 15 mg AFB1/kg(diet).From over 4 million high-quality reads,de novo unigene assembly produced 103,644 fully annotated genes.A total of 1,024 genes were differentially expressed in shrimp fed with AFB1,being involved in functions,such as peroxidase metabolism,signal transduction,transcriptional control,apoptosis,proteolysis,endocytosis,and cell adhesion and cell junction.Upon AFB1 challenge,there were severe histological alterations in shrimp hepatopancreas.R-cells of shrimp fed with AFB1 showed decreased numbers and atrophy.In shrimp fed with AFB1,there was a separation between the myoepithelial layer and the epithelium of the hepatopancreas,and star-shaped polygonal structures of the lumen disappeared in some individuals.In addition,there was an excess of fat in many vacuolated cells,nuclear pyknosis,cell lysis,and cell necrosis.AFB1 challenge increased the activity of several antioxidant enzymes.Our data contribute to improve the current understanding of host-AFB1 interaction,providing an abundant source for identification of novel genes.We believe that the transcriptome information presented in this study will be of great value in understanding shrimp immunity,and in molecular toxicological studies.Furthermore,the vast number of transcripts obtained in this study provides a strong basis for future genomic research on shrimp.