The Genetic Basis Of Hydrophilic Metabolites In The Breast Muscle Of Ducks

China,holding the title of the world’s largest producer and consumer of duck meat,accounts for approximately 80% of the global rearing volume.With an annual output of around 4 billion ducks,meat production in China surpasses 10 million tons,positioning duck meat as the country’s third most consumed meat,following pork and chicken.However,the relentless pursuit of growth rate in meat duck breeding over the past few decades has overshadowed the importance of meat quality,leading to a decline in flavor and overall quality of fast-growing large-sized meat ducks.Therefore,there is a pressing need to intensify research on the genetic mechanisms underlying meat duck quality traits.Exploring majoreffect genes with significant breeding value becomes paramount,alongside establishing an efficient breeding system that combines conventional breeding techniques with molecular breeding approaches.This approach aims to foster the development of high-efficiency,high-quality duck varieties with independent intellectual property rights,thereby presenting a crucial opportunity for revitalizing the seed industry.Meat,which refers to the skeletal muscles of vertebrate animals after slaughter,holds a significant role in human evolutionary history and is widely recognized as an essential component of a healthy and balanced diet due to its rich nutritional content.Being a complex food,the biochemical characteristics of meat are influenced by a diverse array of metabolites present within it.The hydrophilic metabolites in meat,in particular,not only provide essential nutrients but also act as precursors for flavor,directly impacting the aroma of cooked meat.Despite the crucial role they play,little is currently understood about the genetic and biochemical foundations of hydrophilic metabolites in meat.This knowledge gap poses challenges for improving meat quality in livestock and poultry.Therefore,unraveling the genetic and biochemical basis of hydrophilic metabolites in meat holds great significance,as it will provide a fundamental theoretical framework for enhancing the genetic enhancement of meat quality in livestock and poultry.To address this knowledge gap,this study focused on a population of 423 Pekin duck × Liancheng duck gradient 7-line hybrids.The hydrophilic metabolites in the breast muscle of these ducks at 6 weeks of age were identified and quantified using high-performance liquid chromatography-mass spectrometry(LC-MS).Simultaneously,a dataset of genome-wide single nucleotide polymorphism(SNP)sites was obtained through whole-genome resequencing.By performing metabolite-genome-wide association analysis(m GWAS),the study aimed to detect the genetic basis underlying the hydrophilic metabolites in the pectoralis muscle.The results of m GWAS facilitated the identification of candidate genes and potential causal variations that impact the content of hydrophilic metabolites in the breast muscle.Using an advanced approach combining extensive targeted metabolomics technology and highperformance liquid chromatography-mass spectrometry,this study conducted an analysis of 6-week-old breast muscle samples from a population of 423 Pekin duck × Liancheng white duck gradient 7-line hybrids.A thorough examination resulted in the detection of a total of 2481 hydrophilic metabolites,ensuring the quality of the dataset.To assess the genetic regulation of hydrophilic metabolites in the breast muscle,a heritability analysis was performed.Remarkably,it was observed that 25.04% of the hydrophilic metabolites exhibited a generalized heritability greater than 0.5,indicating a substantial genetic influence on these metabolites.Furthermore,the identification of crucial metabolites and volatiles in duck meat unveiled 87 significant compounds,including betaine,nicotinamide mononucleotide,and 2-pyrrolidone.These findings shed light on the important constituents contributing to the flavor profile of duck meat.Moreover,the study investigated the transformation patterns of metabolites and volatiles before and after heating.Notably,the overall correlation between hydrophilic metabolites and volatile compounds was found to be weak.However,glycerophospholipids emerged as vital precursors for volatile compounds,underscoring their role in flavor development.Overall,this research provides valuable insights into the genetic regulation and composition of hydrophilic metabolites in the breast muscle of ducks,facilitating a deeper understanding of the flavor profile and potential mechanisms influencing meat quality.By conducting m GWAS analysis,this study successfully identified a total of 1696 m GWAS signals,which accounted for 17.21% of the hydrophilic metabolites examined.Notably,these GWAS signals were primarily concentrated in the genomic hot spots of chromosomes 2,7,and 28 within the duck genome.Further investigation of these hot spots revealed that 52.14% of them exhibited significant genetic differentiation.Based on comprehensive analysis involving linkage disequilibrium(LD),gene annotation,prior knowledge,and gene expression information,a total of 24 candidate genes were identified as crucial factors influencing the levels of hydrophilic metabolites in meat.Most of these candidate genes were associated with the synthesis or metabolic processes of various substances.One intriguing finding was the joint regulation of carnosine and anserine,which play essential roles in antioxidant activity,anti-aging effects,fatigue resistance,and muscle strength enhancement.The genes GADL1 and CARNMT2 were found to have shared regulatory influence over the content of these two metabolites.Additionally,the study uncovered that the AOX1 gene regulates the content of 2-pyrrolidone,a volatile substance that imparts a marshmallow or maple syrup flavor upon heating.Furthermore,the AADAT gene was identified as a regulator of 2-aminoadipic acid content,which influences lipid metabolism and insulin resistance.Moreover,leveraging the m GWAS results,the study successfully annotated seven previously unknown metabolites,thereby expanding the existing database of hydrophilic metabolites present in the breast muscle.These findings collectively enhance our understanding of the genetic mechanisms underlying hydrophilic metabolites in meat,shedding light on their potential roles in flavor development and physiological effects.This study has not only successfully identified a substantial number of candidate genes that influence the content of hydrophilic metabolites in the breast muscle but has also contributed valuable insights into the genetic underpinnings of these metabolites in skeletal muscle.