| Numerous studies have shown that the differences in meat production traits among pigs with different growth rates are regulated by various gene types,including m RNA,mi RNA,and lnc RNA.The use of hybrid population separation to screen differentially expressed genes and pathways in the longissimus dorsi muscle tissue of individuals with different growth rates at the transcriptional level plays an important role in exploring the molecular mechanisms regulating muscle growth and meat quality traits in pigs.This study first utilizes Duroc × Bamaxiang pig hybrid F2 segregated population,select four individuals with a fast growth rate(high group)and four individuals with a slow growth rate(low group)for slaughter,measure their body size traits,carcass traits,meat quality traits,blood physiological indicators,and plasma biochemical indicators,and analyze the differences in phenotypic traits and physiological metabolism between high and low groups.Secondly,to explore and analyze the differences in muscle histological characteristics and different distribution of myofiber types in different groups leading to differences in meat quality.Finally,transcriptome sequencing was used to screen for differentially expressed m RNA,mi RNA and lnc RNA betweenhigh and low groups,and to explore functional candidate genes and regulatory pathways affecting pig meat production traits.The main results of this article are as follows:(1)Duroc × Bamaxiang pig hybrid high and low groups analysis of differences in phenotype and physiological and biochemical indicatorsThe results of production performance measurement showed that the growth rate of the high group was significantly higher than that of the low group in terms of live weight,body length,body height,chest circumference,tube circumference,abdominal circumference,total visceral weight,heart weight,spleen weight,kidney weight,liver weight,left plate oil weight,front hoof weight,rear hoof weight,head weight,carcass weight,straight length,oblique length,bone weight rate,skin thickness,and eye muscle area before slaughter(P<0.05);The growth rate of backfat thickness in the high group was significantly lower than that in the low group(P<0.05).The results of meat quality indicators showed that the p H48 h,and flesh colour b48 h was significantly higher in the high group than in the low group(P<0.05),while the intramuscular fat and flesh colour L45 min were significantly higher in the low group than in the high group(P<0.05),Intramuscular fat and L45 min was significantly higher in the low group than in the high group(P<0.05).The results of serum biochemical indicators showed that the low group had significantly higher levels of total protein,cholesterol,and creatine kinase activity than the high group(P<0.05),with no significant differences in other biochemical indicators between the high and low groups..The results of blood physiological indicators showed that the low lymphocyte ratio group was significantly higher than the high group(P<0.05),the low platelet count group was extremely significantly higher than the high group(P<0.01),and the high granulocyte ratio group was significantly higher than the low group(P<0.05).(2)Duroc × Bamaxiang pig hybrid high and low groups comparative analysis of muscle histological characteristics and myofiber types.The results of real-time fluorescence quantitative PCR of RNA in the dorsal longest muscle tissue of individuals in the high and low growth rate groups showed that the expression of My HC2 b gene was significantly higher in the high group than in the low group(P<0.05),while the expression of genes in My HC2 x and My HCI was significantly higher in the low group than in the high group(P<0.05).The HE staining of myofiber sections showed that there was no significant difference in fiber diameter between the high and low groups in the longest dorsal muscle(P>0.05);NADH myocardial flavoprotein activity staining showed that the proportion of type I fibers in the longest dorsal muscle was significantly higher in the low group than in the high group(P<0.05),while the proportion of type II fibers was significantly lower in the low group than in the high group(P<0.05).(3)Duroc × Bamaxiang pig hybrid high and low groups transcriptome analysis of longissimus dorsi muscleThe m RNA sequencing analysis results of the longissimus dorsi muscle tissue in individuals with high and low growth rates indicate that a total of 248 differentially expressed genes were detected,among them,145 were upregulated and 103 were downregulated in the high group;GO enrichment analysis showed that the differential genes were mainly enriched in the development of skeletal muscle,cell proliferation,tissue homeostasis,protein kinase activity,ATP binding,actin binding,cytoplasm,cytoskeleton,and muscle membrane;The results of KEGG enrichment analysis showed that differential genes were mainly enriched in MAPK signaling pathway,PI3K/AKT signaling pathway,and calcium signaling pathway;The results of protein interaction analysis indicate that MTMR14,PYGM,PGAM2,MYH1 and MYH7 may be candidate genes affecting pig meat production traits.The mi RNAs sequencing analysis results of the longissimus dorsi muscle tissue in individuals with high and low growth rates indicate that a total of 25 differentially expressed mi RNAs were detected,among them,16 were upregulated and 9 were downregulated in the high group;GO enrichment analysis showed that differential mi RNAs were mainly enriched in protein phosphorylation,positive regulation of transcription,negative regulation of gene expression,protein kinase binding,RNA binding,m RNA binding,nucleus,cytoskeleton,and cytoplasm;KEGG enrichment analysis found that differential mi RNAs are mainly enriched in some pathways related to the regulation of meat quality and muscle fiber growth,including Hippo signaling pathway,m TOR signaling pathway,and MAPK signaling pathway;Quantitative analysis of the selected mi RNAs revealed that mi R-208 b and mi R-124a-1 may be involved in regulating the transformation of muscle fiber types.The lnc RNA sequencing analysis results of the longissimus dorsi tissue in individuals with high and low growth rates indicate that a total of432 differentially expressed lnc RNAs were detected,among them,324 were upregulated and 108 were downregulated in the high group;GO enrichment analysis revealed that differential lnc RNA target genes were enriched mainly in the negative regulation of cytokine activity,cellular response to lipopolysaccharide,immune response,phospholipid activity,monooxygenase activity,oxidoreductase binding,nucleus,cytoskeleton,and cytoplasm;KEGG enrichment analysis revealed that differential lnc RNA target genes were mainly found to be enriched in the PPAR signalling pathway,fatty acid digestion and absorption.The analysis resulted in the screening of four lnc RNAs associated with meat production traits,including ENSSSCG00000002475,ENSSSCG00000003349,ENSSSCG00000006245 and ENSSSCG00000006875.In order to analyze the regulatory relationship between different RNAs affecting pig meat production traits,correlation analysis was conducted based on the sequencing results of differential m RNA,mi RNA,and lnc RNA to screen out the effects of ce RNA network regulation,including ENSSSCG00000042061-ssc-mir-208b-MYH7,ENSSSCG00000042223-ssc-mir-146a-MTMR14,and ENSSSCG00000045539-ssc-mir-9-3-MYH1.To sum up,in this paper,the molecular basis of meat production performance differences in pigs with different growth rates was systematically analyzed by separating individuals with different meat production traits by hybridization.Using transcriptome,some m RNA,mi RNA,lnc RNA and related metabolic pathways and ce RNA networks differentially expressed between high and low groups were screened,which may be involved in regulating meat production traits and meat quality traits of pigs. |
