Screening Of Heat-resistant Gene And MiRNA Of Holstein Dairy Cows Based On MRNA Sequencing And MiRNA Sequencing

At present,heat stress is one of the main factors restricting the development of dairy industry in southern China.At present,the study of thermal stress of dairy cows was focused on improving feeding conditions and production processes,such as improving the facilities and equipment to improve the climate and adding feed additives to relieve damage from heat stress,while molecular research is much too little relatively.The dairy cow's heat resistance is a quantitative trait which heritability is low,the effect of improvement through breeding is not obvious.The aim of this study is through high-throughput sequencing and bioinformatics analysis to study the different expression of genes and secretory miRNAs of blood between high heat tolerance cows and low heat tolerance cows in heat stress,to reveal the molecular mechanisms of genes and miRNAs in the regulation of heat tolerance of dairy cows,and to find miRNAs,genes related to the enhancement of heat tolerance of dairy cows,which can to provide reference data to research and production practices.In this study,we selected 200 Holstein dairy cows with the same physical health and the same parity in the middle of lactation,then we calculated the rate of decline in milk production in the summer,ten of the cows with lowest decrease level(0.09 ± 0.06)were assigned to high heat-resistance group,and another ten cows with highest decrease level(0.56 ± 0.08)were considered as low heat-resistance group.For the two groups,the blood was collected to test the concentration of the biochemical such as T3?T4?Cor et al,rectal temperature,THI was measured in mid-September(heat stress period)(THI=82.19)and mid-December(non-heat stress period)(THI=50.01),respectively,according to the concentration of T4,highest heat-resistant group(3)and lowest heat-resistant group(3)were selected to extract the blood RNA for follow-up mRNA sequencing and miRNA sequencing.We got the answer:(1)There were 200 significantly different genes between the high heat-resistant group and the low heat-resistant group during heat stress,of which 186 were up-regulated and 14down-regulated.There were 72 significant differences in the heat-resistant group with high heat-resistant group,66 of which were up-regulated and 6 were down-regulated.After the significant differences genes in the summer test of two groups eliminated the same part DEGs between the winter and summer of two trial groups,thereby removing the differential genes caused by the individual genetic background.After which,there were 187 gene that were closely related to heat-resistant properties under heat stress successfully found in Holstein dairy cows,among which there were 177 up-regulated and 10down-regulated.GO analysis showed that the activity of the gene was mainly related to cell process,biological process regulation,immune process,stress response,cell,integration,membrane,nucleic acid transcription factor activity,Protein transcription factor activity,metabolic processes,and catalytic responses.KEGG analysis showed that the main pathway was related to the interaction between cytokines and cytokines,chemokine signaling pathway,TNF signaling pathway,MAPK signal pathway,osteoclast differentiation pathway,P53 signaling pathway,apoptosis and so on.(2)Through deep excavation,we conclude that Holstein dairy cows may resist heat stress by following ways: 1)By upregulating Src,PI3 K,IL-3R,IKB,enhancing cell survival,2)Enhancing the macrophage phagocytosis and tissue repair by up-regulating SLC11A1,CEBPB,IL-B,and 3)By down-regulating mi R-432,miR-320 a,upregulate miR-185 to target gene,promoting cell proliferation,promoting inflammation,protecting cells from apoptosis.