Mechanism Analysis On Beef Quality Variation Induced By Acute Stress

Although much research has been focused on beef tenderness, the mechanisms andfunctional genes of controlling beef quality have yet to be elucidated. In order to gain deepinsight into beef tenderness, in this research, we attempt to explore underlying genes,networks and pathways related to beef tenderness by evaluating the muscle transcriptomicprofiles in Angus cattle with divergent tenderness induced by acute stress. The results areshown below.(1) Beef quality varied significantly after acute stress. The Warner-Bratzler shear force(WBSF) of LD significantly increased after acute stress, and beef tenderness became worse.Fat acid contents of different stress status varied largely also. But the beef quality variationwithin stress group was divergent largely.(2) Agilent bovine4×44bovine microarray was used to analyze LD musles from3control and4stress individuals with highest WBSF. The results showed that137genessignificantly differentially expressed between stress and control groups (P<0.05,|logFC|>1.5,FDR<0.3). Of which,64were up-regulated in stress group compared withcontrol group while73were down-regulated. Cluster analysis, Gene Ontology (Go) Term,and IPA (Ingenuity Pathway Analysis) results showed that these genes functioned ininflammatory response, lipid metabolism, molecular transport, cell-to-cell signaling andinteraction, cellular development, etc. Combine our results and literatures, we concluded thatgenes, such as IL12A, IL13, CCL8, CCL24, CXCL1, ATF3, RCAN1, ADIPOQ, GADD45G,SIM1, NR2F1, ZHX3, GSX2, may play roles in beef quality and anti-stress.(3)miRNA microarray was used to analyze the miRNA expression profiles between3control and3stress with highest WBSF. Microarray and qRT-PCR results showed that bta-miR-497was over-expressed in stress group compared to control group.1160genes werepredicted as this miRNA's regulation targets using bioinformatic tools. Combined with Oligomicroarray, in these target genes,70were differentially expressed. These70genes wereinvolved in protein autophosphorylation, actin cytoskeleton organization, cerebral cortex cellmigration, actin filament-based process, retinoic acid receptor signaling pathway, endoplasmic reticulum organization, protein phosphorylation, etc. We concluded that miRNAinfluenced beef quality by regulating target genes and bta-miR-497may play some roles inbeef quality and stress-resistant.(4) DNA methylation level in promoters of differentially expressed genes significantlyvaried after acute stress. Gene expression was negatively associated with DNA metylationlevel. This confirmed that DNA methylation in promoter represses gene expression. Weinferred that DNA methylation may involve in beef quality varation in this experiment. Wealso found the change of DNA methylation in blood. This just gave us a clue that DNAmethylation lelvel in bovine blood may be a biomarker for beef quality and stress status.(5) Beef quality varied largely within stress group. Microarray was used to analyzetender and tough groups. We found53genes (EST) were significantly differentially expressed.Of which,27were up-regulated in tough group compared to tender group while26weredown-regulted. These genes were involved in lipid metabolism, etc. We concluded thathydrolase, peptidase, GTPase activity, lipid metabolism, small molecule biochemistry,molecular transport, and tissue development were related with beef quality variation. Weinferred that genes, such as FABP4,SCD,FASN,THRSP,MYH3, MYH8,GBP1,GBP3,GBP5,GBP6,GBP7, could be candidate genes for beef quality and tenderness.