Biological Characterization And Expression Regulation Of Elongases Of Very Long Chain Fatty Acids(ELOVL) Gene Family In Chicken(Gallus Gallus)

Elongases of very long-chain fatty acids(Elovl)catalyze the rate-limiting condensation step in the elongation of fatty acids including LCPUFA biosynthesis.Although in mammals,the function and regulation mechanisms of this gene family,especially individual members such as ELOVL2,ELOVL5,and ELOVL6,have been studied in depth,studies on the ELOVL gene family in poultry have rarely been reported.In order to study the biological characteristics and expression regulation mechanism of the chicken ELOVL gene family,this study used the green shell chicken as the experimental material.Firstly,bioinformatics analysis was used to systematically analyze the origin,evolution and protein domains of chicken ELOVL gene family members.Secondly,the temporal and spatial expression patterns of the ELOVL gene family in laying hens were studied using PCR and q PCR technology.Then,the expression regulation mechanism of ELOVL gene family was studied by using estrogen treated young chicken and chick embryo liver primary cell models.Finally,the regulation mechanism of mi RNA on the expression of ELOVL5 in the liver was analyzed by using the dual luciferase reporter system and gene overexpression and interference techniques.The main experimental results are as follows: 1.Origin,evolution and protein structure characteristics of chicken ELOVL gene family.The chicken ELOVL gene family has 7 members,both of which have the typical ELO domain of the very long-chain fatty acid elongase family and the family's representative motif(HXXHH),which may be its active center.Among them,ELOVL3 and ELOVL6 have 6 transmembrane regions,and other members have 7 transmembrane regions.The analysis of the origin and evolution of the ELOVL gene family showed that ELOVL gene family is clustered into two major branches.Among which,the origin and evolution of ELOVL3 and ELOVL6 are close and belong to the same homologous genes,and the function is similar.In the other large branch,the origin and evolution of ELOVL2 and ELOVL5,ELOVL1 and ELOVL7 genes are close,and they are also similar homologous genes,and they have similar functions respectively.ELOVL4 is closely related to the origin and evolution of ELOVL2 and ELOVL5 genes,independently originating from an ancient gene,is related to ELOVL2 and ELOVL5.Further genomic synteny block analysis showed that the origin and evolution of the ELOVL3 gene are highly conserved in birds,and the other members are highly conserved in higher vertebrates.ELOVL gene family have poor conservation in fish and other lower vertebrates,indicating that ELOVL gene family members may originate from different ancient genes.2.The temporal and spatial expression pattern of ELOVL gene family in the layers of chickens.The ELOVL1,ELOVL5,ELOVL6 and ELOVL7 genes in the chicken ELOVL gene family are widely expressed in all tissues without tissue specificity,which is related to the extensive presence of saturated fatty acids in the body.ELOVL2 gene was significantly enriched in the liver.ELOVL3 gene was highly expressed in the lung.ELOVL4 gene was not expressed in the 10-week-old liver,glandular stomach,and abdominal fat,and in the 30-week-old liver,heart,and breast muscle.The expression analysis of chicken ELOFL gene family in liver,kidney and abdominal adipose tissue at different developmental stages found that in the liver tissue,the expression level of ELOVL1 gene in the early stage of growth(5 week-old)was significantly higher than other developmental stages(p<0.05).It may be related to the early growth and development of laying hens.The expression levels of ELOVL2,ELOVL5 and ELOVL6 genes at the peak of egg production(30-week-old)and 35-week-old are significantly higher than those of other developmental periods(p<0.05).It is due to the vigorous metabolism of fat during the laying period and the body's demand for fatty acids was increase.The expression levels of ELOVL7 gene in liver tissue,kidney tissue,and abdominal adipose tissue at different developmental stages were significantly increased only at 35 weeks of age(p<0.05),while the expression levels of other members in kidney and abdominal fat at different developmental stages were not significant.3.Expression regulation mechanism of ELOVL gene family.Estrogen treatment significantly decreased the expression level of ELOVL1 gene in liver tissue and chicken embryo liver primary cells(p<0.05),while the expression levels of ELOVL2,ELOVL4,ELOVL6 and ELOVL7 genes were significantly or very significantly up-regulated(p<0.05 or p<0.01),but there was no significant effect on the expression of ELOVL3 and ELOVL5 genes.It indicated that estrogen can regulate the expression of ELOVL1,ELOVL2,ELOVL4,ELOVL6 and ELOVL7 gene in ELOVL gene family.4.Mi RNAs regulate the expression of ELOVL5 gene.Bioinformatics analysis was used to predict mi RNAs interacting with ELOVL5 gene.The mi RNA transcriptome database of the 20 week old /30 weeks old group was confluence analyzed.The potential target mi RNA-218-5p for ELOVL5 gene was identified.The target relationship between ELOVL5 gene and mi RNA-218-5p was verified by dual fluorescence reporter system.It is proved that under normal physiological condition,the expression of ELOVL5 gene is regulated by mi RNA-218-5p at post-transcriptional level.In summary,the chicken ELOVL gene family have the same functional domain,can catalyze the elongation reaction of fatty acids,and each member is highly conserved in the evolution process.The expression patterns of ELOVL gene family in various tissues are not the same.It was demonstrated that each member played an important role.The expression of ELOVL1,ELOVL2,ELOVL4,ELOVL6 and ELOVL7 genes was regulated by estrogen in chicken liver,and the expression of ELOVL5 gene was regulated by mi R-218-5p at post-transcriptional level.