| The innate immune system is a non-specific mechanism with rapid response,which plays a very important role in the early defense of animals against the invasion of foreign pathogens.Acute phase response（APR）is an important part of animal innate immunity.It is a rapid response of organisms to infection,tissue damage and immune system diseases and other pathological reactions.Acute phase protein（APP）is a type of protein that undertakes the main immune task in the APR process.Serum amyloid A is a conservative acute-phase protein,which is often used as a physiological indicator to evaluate the degree of inflammation in animals.In the first part,we used the aquaculture species as experimental materials to identify its serum amyloid PcSAA.The amino acid sequence of PcSAA includes a typical signal peptide and a conserved SAA domain.PcSAA expression level,after stimulation by White spot syndrome virus（WSSV）,Gram-positive bacteria Staphylococcus aureus and Gramnegative bacteria Aeromonas hydrophila,was significantly up-regulated and reached a peak at 24 h.In order to further study the function of PcSAA,we used siRNA for RNA interference,knocked down the expression of the gene,and found that the ability of crayfish to cope with viral and bacterial infections was significantly reduced,and the mortality rate was significantly increased.Further research found that the recombinantly expressed rPcSAA can bind to the envelope protein VP28 on the surface of WSSV.In addition,rPcSAA can also bind to polysaccharides on the surface of bacteria or directly bind to bacteria.Our histological analysis of the intestines of crayfish found that compared with the control group,after inhibiting the expression of PcSAA,the intestinal epithelial cells of the crayfish infected by bacteria and viruses were arranged disorderly,a large number of vacuoles appeared in the lamina propria,and the stratum corneum on the surface of epithelial cells appeared to fall off.The above results showed that PcSAA can respond to viral and bacterial stimuli by combining polysaccharides on the surface of bacteria and envelope proteins on the surface of viruses to help the body resist external pathogens.In addition,we also discovered a stress-related protein Turandot from Marsupenaeus japonicus,named MjTot.This was the first time such a protein had been identified in a crustacean.We found that after WSSV stimulation,the expression level of Mj Tot was significantly up-regulated and reached a peak at 48 h.We also used RNA interference and recombinant protein injection to explore the antiviral function of MjTot.When the expression of MjTot was inhibited,the virus content in the shrimps and the mortality of the shrimps increased significantly.When the recombinant protein rMjTot was injected into the shrimps,the virus content in the shrimps was significantly reduced.We further screened the anti-lipopolysaccharide factor ALFs in shrimps and found that MjTot can induce the up-regulation of ALF-C1 and ALF-C2.Finally,we explored the relationship between MjTot,ALF and Stat.It was concluded that MjTot may play an antiviral role by regulating Stat and then ALF. |
