| The oriental river prawn,Macrobrachium nipponense,is an important freshwater economic aquaculture species in China.In the aquaculture process of M.nipponense,the feed input commonly cost accounts for more than 50% of the total input cost.Improving the feed conversion efficiency of M.nipponense can not only improve economic benefits,but also save food and reduce the impact of aquaculture wastewater on the environment.Therefore,improving the feed conversion efficiency is of great significance to aquaculture.Feed conversion efficiency traits are important economic traits of aquatic animals.Common indicators to measure feed conversion efficiency in production mainly include feed conversion ratio(FCR),feed conversion efficiency ratio(FER)and residual feed intake(RFI).Practice has proved that RFI is more suitable for aquatic animals than FCR and FER in the process of genetic improvement of feed conversion efficiency traits of aquatic animals.At present,the molecular mechanism and pathway of RFI trait regulation in economic crustaceans have not been fully analyzed.This study analyzed and explored the results of the key regulatory genes and pathways of feed conversion efficiency traits in M.nipponense by identifying different RFI subgroups,using transcriptome and metabolomics techniques,and discussed the differences of growth traits and enzyme activity characteristics of M.nipponense with different feed conversion efficiency.The main results of this study are as follows:(1)After 75 days of cultivation of M.nipponense and grouping according to RFI value,it was found that the individual feed utilization efficiency of low residual feed intake group(LRFI group)was higher than that of high residual feed intake group(HRFI group),and the individual average daily feed intake difference was 0.0098 g.The experimental data showed that there was no significant difference between HRFI group and LRFI group in average daily growth(ADG)and average daily growth body length(ADGBL).At the same time,the RFI value of individuals in the two groups was significantly correlated with daily feed intake(DFI),but there was no significant correlation between RFI and growth indicators such as ADG and ADGBL.The improvement of M.nipponense feed efficiency traits RFI is achieved by changing the DFI while the ADG is unchanged.(2)The hepatopancreas and muscle of the M.nipponense from the HRFI and LRFI groups identified after 75 days of culture were sequenced by transcriptome sequencing technology,and the changes of molecular response and pathway after grouping with different RFI values under long-term feeding conditions were studied.The results showed that 77.81 G of Clean Data was obtained,4540 differentially expressed genes(DEGs),such as cathepsin B,carboxypeptidase,and cytochrome P450 family,were identified in the liver and pancreas;3894 DEGs were identified in muscles,such as pyruvate kinase,6-phosphate fructose kinase,and α-Amylase,etc.Through GO(Gene ontology)analysis and KEGG(Kyoto Encyclopaedia of Genes and Genomes)enrichment analysis of DEGs,it was found that these identified DEGs were enriched in GO pathways related to oxidation,decomposition,and energy generation in the hepatopancreas and muscles during GO analysis.These pathways mainly involve aerobic respiration,carnitine catabolism,mitochondrial electron transport,cellular lipid catabolism,and positive regulation of innate immune responses.The identified DEGs are enriched in some KEGG pathways related to nutrient metabolism in the hepatopancreas and muscles during KEGG analysis.These pathways include carbohydrate digestion and absorption,protein digestion and absorption,and sphingolipids metabolism.The differences in these metabolic pathways may have a certain impact on the RFI traits of M.nipponense.(3)Non-targeted metabonomics technology was used to identify the differentially expressed metabolites(DEMs)of hepatopancreas and muscle of M.nipponense from HRFI and LRFI groups identified after 75 days of culture.445 and 247 kinds of DEMs were identified in hepatopancreas and muscle of M.nipponense respectively.In addition,metabolic pathways such as arginine biosynthesis,lysine biosynthesis,aminoacyl-t RNA biosynthesis,and purine metabolism are significantly enriched in the liver and pancreas,while metabolic pathways such as pyrimidine metabolism,glutathione metabolism,nitrogen metabolism,and m TOR signaling pathway are significantly enriched in muscles.The metabolomics analysis showed that the metabolism of amino acids,lipids and nucleotides significantly affected the feed conversion efficiency of M.nipponense.(4)Based on KEGG database,the metabolic pathway enrichment analysis of DEGs and DEMs was performed in hepatopancreas and muscle.Among them,compared with LRFI group,HRFI group was enriched in the three KEGG pathways of glycerol phospholipid metabolism,ether lipid metabolism and aminoacyl-t RNA biosynthesis in the transcriptome and metabolomic analysis and joint analysis of hepatopancreas.The glutathione metabolic pathway was enriched simultaneously in the transcriptome and metabolome of two different groups of muscle and in the combined omics analysis.Trypsin(PRSS1＿2＿3)enriched in the hepatopancreas and muscle of the transcription group in HRFI group and LRFI group,α-The activity of amylase(AMY1A)and hexokinase(HK)in HRFI group was lower than that in LRFI group,which was consistent with the low expression of corresponding genes in the transcriptome.The results of this study showed that the M.nipponense from the differential RFI group(HRFI group and LRFI group)had different regulatory ability and metabolic process.The down-regulated genes,such as carboxypeptidase A1,6-phosphofructokinase,long-chain-acyl-Co A dehydrogenase,et.al.,in digestion and absorption of nutrients,and the up-regulated metabolites,such as aspirin,lysine,et.al.,in response to immunity could be potential candidate factors contributed to RFI variation for M.nipponense.In conclusion,these results will provide new insights into the molecular mechanism of feed conversion efficiency,and contribute to selective breeding to improve the feed conversion efficiency of M.nipponense. |
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