| Fat constitutes a crucial nutrient for fish,endowing them with indispensable fatty acids and energy,while assuming a pivotal responsibility in their growth and metabolism.Despite its paramount importance,the precise regulatory mechanism underlying fish fat metabolism remains nebulous.To address this knowledge gap,goldfish featuring conspicuous variations in their body tissue fat content were enlisted as experimental subjects in this study.Through the utilization of transcriptome and proteomic analyses,the metabolic pathways that underlie fish fat deposition were explored,thereby laying a theoretical foundation for unraveling the molecular regulatory mechanism of fish fat metabolism.This study entailed the measurement of the fat content in eight distinct goldfish(CJ,WT,HT,SP,LJ,PS,ST,HDH),with a particular focus on the White Oranda with Red Cap(HDH)goldfish and the Pearl scale goldfish(PS),both of which exhibited substantial differences in their hepatopancreas fat content.Subsequently,by means of a comparative analysis of transcriptome and proteome sequencing,differential genes and proteins relevant to fat metabolism were identified in the hepatopancreas of the two goldfish species under consideration.Finally,the gene expression patterns during embryonic development of the two goldfish species were explored via transcriptome sequencing.The primary findings are as follows:1.The fat content of eight distinct goldfish species was ascertained,and it was discovered that significant differences in both fat deposition location and content existed among them(P<0.05).This observation lends support to the notion that the regulatory mechanism of lipid metabolism varies across goldfish species.Among them,the fat content of PS in whole fish,abdominal muscle,dorsal muscle and visceral mass was significantly higher than that of HDH(P<0.05),but it was significantly lower than that of HDH in hepatopancreas(P<0.05).Examination of serum biochemical indices revealed that compared to the PS,the HDH displayed notably lower activity levels of high-density lipoprotein and low-density lipoprotein,whereas their activities of glutamic pyruvic transaminase,glutamic oxaloacetic transaminase,and lactate dehydrogenase were significantly higher(P<0.05).Further inspection of the hepatopancreas biochemical indices of HDH and PS goldfish indicated that the level of hepatopancreas bile acid in the PS was significantly greater than that in the HDH(P<0.05),potentially promoting the breakdown of hepatopancreas fat in PS goldfish.Furthermore,the level of free fatty acids in the hepatopancreas of PS goldfish was markedly higher than that in HDH(P<0.05),thereby lending additional support to the aforementioned supposition.2.Transcriptome sequencing served as a valuable tool for investigating hepatopancreatic lipid metabolism in HDH and PS.In the analysis of hepatopancreas tissue,a total of 3174 differential genes were identified,consisting of 1406 up-regulated genes and 1786 down-regulated genes.GO annotation analysis revealed that the DEGs were primarily annotated to ’peptidase inhibitor activity’,’ peptidase regulator activity’,’enzyme inhibitor activity’,’oxidation reduction process’,’energy reserve metabolic process’,’metabolic process’,and ’extracellular region’.KEGG functional analysis demonstrated that the key metabolic pathways associated with the DEGs were ’carbon metabolism’,’PAR signaling pathway’,’phenylalanine metabolism’,and other biological processes.Furthermore,within the PPAR signaling pathway,seven genes closely linked to fat metabolism were identified,namely PPARα,ApoAI,CYP27A1,FATP1,LPL,ACS,CYP8B1.These genes exhibited notable differences in the hepatopancreas of the two goldfish species,indicating that they may serve as the principal genes responsible for the variance in lipid metabolism in the hepatopancreas of these two species of goldfish.The expression levels of multiple genes were verified by qRT-PCR to be significantly different in the hepatopancreas of the two goldfish(P<0.05),suggesting that these genes may play a vital role in the differentiation of fat metabolism between the two species.3.A proteomic analysis of the hepatopancreas of HDH and PS was conducted,and it revealed the identification of 816 differential proteins(DEPs),with 427 up-regulated in HDH goldfish and 389 in PS goldfish.GO annotation analysis indicated that the DEPs were mainly annotated to ’iron ion binding’,’heme binding’,’ion binding’,’oxidation reduction process’,’carbohydrate derivative catabolism’,and ’thyroid hormone transport’.KEGG functional analysis demonstrated that the key metabolic pathways associated with the DEPs were ’Primary bile acid biosynthesis’,’Chemical carcinogenesis’,’Metabolism of xenobiotics by cytochrome P450’,and other biological processes.Among them,the expression of 9 proteins changed significantly(P<0.05).These proteins were involved in various pathways,including bile acid metabolism(CYP7B1 and HSD3B7),carbohydrate digestion and absorption(AMY2A and LPH),taurine and sulfinic acid metabolism(CSAD and CDO1),and steroid metabolism(EBP and Msmol).It is suggested that these proteins may play a critical role in regulating the hepatopancreatic lipid metabolism in both goldfish species.4.A comparative transcriptome analysis was conducted to identify differentially expressed genes between HDH and PS embryos at 0h,48h,and 5d stages.The results revealed a significant number of differentially expressed genes among embryos of the same species at different stages.For instance,in HDH,33,768,15,088,and 35,966 differentially expressed genes were identified at 48hvs0h,5dvs48,and 5d 5dvs0h stages,respectively.Similarly,34,373,18,268,and 36,901 differentially expressed genes were found in PS Goldfish at the three stages,respectively.The findings from the transcriptome analysis suggest that there are complex regulatory mechanisms involved in the development of goldfish embryos,with a large number of genes differentially expressed at different stages.The enrichment of up-regulated genes in the PPAR signaling pathway between 48h to 5d suggests that there are significant changes in fat metabolism during this developmental period in both HDH and PS embryos.However,the lack of significant differences in lipid metabolism-related pathways between the two goldfish embryos at the same time suggests that any differences in lipid metabolism may be due to factors such as feed utilization rather than genetic differences between the two varieties.Overall,these findings provide insights into the molecular mechanisms underlying the development of goldfish embryos and may have implications for understanding the regulation of lipid metabolism in these fish. |
