The Roles Of DHA And ARA For Apostichopus Japonicus Under Cold And Immunity Stress And Analyzation Of The Regulatory Mechanisms

As the Holothroidea class of Echinodermata,Apostichopus japonicus is an important aquaculture species of northern my country.The overwintering-period is high incidence period for A.japonicus diseases which seriously affectes the development of the economy.the experiment found the survival rate of A.japonicus by cold stress and immune stress was significantly reduced.This indicates that the immune ability of A.japonicus by cold stress is greatly reduced.Therefore,systematic screening of key factors affecting the immune function(cold and immune stress)of A.japonicus during is of great significance for the healthy breeding of overwintering-period during the overwintering-period.The metabonomics was used to analyze the changes of the metabolites of A.japonicus by low temperature stress/immune stress,the experiment screened out 409 different metabolites.21 kinds of significantly different metabolites were screened in the low temperature stress group,and 36 kinds of significantly different metabolites were screened out in the immune stress group,Among them,lysophospholipid significantly up-regulated under the two stresses.This indicates that lipids play an important role in the cold and immune stress of A.japonicus.Since polyunsaturated fatty acids are an important part of lysophospholipids,The experiment uses GC-MS to detect the composition of fatty acids of A.japonicus by low cold stress/immune stress,the results showed that ARA content of A.japonicus was up-regulated when infected with Vibrio splendidus,ARA content of A.japonicus by cold stress was not up-regulated,but DHA was significantly up-regulated.As the first cold stress and then immune stress,it found that the ARA content of A.japonicus is no longer up-regulated.This indicates that the metabolic imbalance of DHA/ARA is an important reason for the immunity decreased of A.japonicus by cold stress.The experiment further analyzed the molecular mechanism of A.japonicus responding to cold/immune stress to regulate the ARA/DHA metabolic imbalance.The polyunsaturated fatty acid elongase Aj-Elovl5 is the key enzymes for the synthesis and metabolism of ARA and DHA of A.japonicas,the experiment uses q RT-PCR to detect the expression of Aj-Elovl5 of A.japonicas by cold stress/immune stress,and the results showed that the transcription level of Aj-Elovl5 of A.japonicas by cold stress was significantly up-regulated,and the expression of Aj-Elovl5 of A.japonicas by immune stress was down-regulated.This indicates that Aj-Elovl5 participates in the regulation of the synthesis of ARA and DHA in cold and immune stress,and plays an important role in the synthesis of DHA.The experiment uses RNAi technology to silence Aj-Elovl5 of A.japonicas,the results showed that the DHA content of A.japonicas silenced was down-regulated,and further treated the silenced A.japonicas with cold stress,found that the content of DHA was not significantly up-regulated,and shows that Aj-Elovl5 involved positive regulating DHA synthesis of A.japonicas,and up-regulat expression of DHA during cold stress.However,how A.japonicas regulates the metabolic synthesis of ARA under dual stress needs to be further studied.Above results show the metabolic imbalance of DHA/ARA is an important reason for the immunity decreased of A.japonicus by low temperature stress,A.japonicus regulates the expression of Aj-Elovl5 to regulate the metabolism and synthesis of DHA of A.japonicus by low temperature and immune stress.