Molecular Mechanisms Of Meat Quality Changes In Da-heng Broilers At Different Developmental Stages Based On Metabolome And Transcriptome

In recent years,an intense genetic selection for poultry growth rate,reproductive performance,feed utilization had led to progressive improvements.However,these advances have been often accompanied by deterioration of the broiler meat quality,including high incidence of muscle abnormalities,such as white striping and wooden breast.Therefore,how to improve the quality of poultry meat while maintaining its production performance has become a difficult problem for the development of the poultry industry.In this study,the Daheng broilers at different developmental stages were used to comprehensively and systematically explored the effect of age on meat quality from the aspects of physical,chemical,histological and sensory properties.Metabolome technology was applied to explore the age-dependent dynamic change of metabolites in chicken meat and identify the metabolites and metabolic pathways that play a key role in meat quality.Transcriptome technology was applied to study the temporal expression profiles of chicken meat from 60 days of age to 180 days of age,and determine potential genes or gene modules influencing intramuscular fat deposition,fatty acid composition,and volatile compounds.Integration analysis of metabolome and transcriptome profiles determined the potential genes that affect the accumulation of specific metabolites at different stages.Finally,the potential gene related to intramuscular fat deposition was selected for function analysis in intramuscular preadipocyte.These results would provide a theoretical basis for revealing the genetic mechanism of the chicken meat quality change and applying for molecular breeding for high-quality broilers.The results of the study are as follows:(1)During chicken growth and development,meat quality changes significantly.Older chickens presented a higher p H,shear force,redness,muscle fiber diameter,fiber area,intramuscular fat content but lower yellowness and fiber density.As age increased,the fatty acid composition changed gradually,while the changes of volatile flavor compounds fluctuated greatly.Intramuscular fat was significantly correlated with only three volatile flavor compounds,indicating that the generation of volatile compounds was more dependent on the fatty acid composition rather than total intramuscular fat content.(2)A total of 573 metabolites were identified in chicken meat.Generally,pentadecanoic acid,stearic acid,creatine,carnosine,IMP,L-histidine and L-isoleucine presented an upward trend with age,while anserine,DHA,L-aspartic acid,LPA 18:1 and LPI 18:1 decreased with age.The content of EPA,L-glutamate,LPI 20:4,phosphocreatine,and taurine fluctuated among five age stages.According to metabolic composition,180-day-old chicken meat had the best antioxidant,umami and nutritional value.The main pathways of chicken meat metabolism affected by age were fructose and mannose metabolism,arachidonic acid metabolism,steroid hormone biosynthesis,riboflavin metabolism,biosynthesis of unsaturated fatty acids,and linoleic acid metabolism.(3)A large number of differential genes between different age groups were screened by RNA-seq.STEM analysis identified a total of 12 distinct temporal gene expression patterns,of which ME 11 were gradually upregulated with age while ME 2showed a downregulated tendency with age.Gene co-expression network analysis showed that the fatty acids content was more correlated with those genes that were gradually upregulated or downregulated with slaughter age,while the volatile flavor compounds were more correlated with the genes that fluctuated with slaughter age.Integration analysis of metabolome and transcriptome profiles indicated that genes such as GART,ALDH6A1,MFSD2 A,DGAT2,NAMPT,CYP3A4,LIPA,GALM,IL4I1,PIK3 CG,CYP2D6,PLTP and PNMT were responsible for the age-dependent accumulation of metabolites.These potential candidate genes for meat quality could be verification for further studies.(4)This study found that MFSD2 A could promote the proliferation and migration of chicken intramuscular preadipocytes as well as promote the differentiation and lipid droplet formation of chicken intramuscular preadipocytes through the PPAR signaling pathway.To sum up,this study explored the changes of meat quality and key metabolites related to meat quality in breast muscle tissue during the growth and development of chickens(60,90,120,150,and 180 days old)at the tissue and cell levels.The key genes of intramuscular fat deposition and functional verification on chicken intramuscular fat cells provided a scientific theoretical basis for further improving chicken meat quality,and also for in-depth exploration of the molecular mechanism of intramuscular fat deposition.