Identification,Classification And Transcriptome Analysis Of Olfactory Receptor Genes In Sheep

Olfactory plays an important role in animal life activities.Animals rely on olfactory perception of environmental chemical molecules to obtain outside information,help identify food,avoid danger,and pursue spouses and other behaviors.The specific binding of the olfactory receptor to the odor is the first step in the animal's recognition of the odor.The olfactory receptor is encoded by a large number of olfactory receptor genes and is called the olfactory receptor superfamily in the genome.Studies have shown that the number of olfactory receptor genes and the rate of pseudogenes are the main factors affecting the olfactory ability of animals.Mammalian olfactory receptor gene profiles rapidly evolved between different species in order to adapt different ecological environments,causing significant birth and death events(birth and death).Sheep,as a representative animal of the ruminant mammals of the cloven-hoofed pheasant,the olfactory not only effect its feeding,but also effect the unique "ram effect",maternal behavior and offspring recognition in the breeding behavior.However,the olfactory recognition mechanism is still not clear.Although relevant studies have provided an in-depth understanding of the anatomical structure of the nasal olfactory epithelium of sheep,the olfactory receptor genome sequence and its expression in sheep are rarely known at present.With the development of DNA sequencing technology,the sequencing accuracy is getting higher,the coverage is getting larger,and the genome sequence is better,which makes it available to use the sheep genome data and high-throughput sequencing technology to analyze the olfactory receptor gene sequence and expression.In this study,several genomic sequences were identified by genomic sequence to identify the olfactory receptor gene sequence of sheep,and the transcriptome high-throughput sequencing was used to analyze and verify the expression of olfactory receptor gene in sheep.The main findings include:1.The olfactory receptor gene was identified from the sheep genome,and 1983 OR genes were identified,including 929 functional genes and 1053 pseudogenes,and a truncated gene located near the genome gap.These genes are distributed on 91 gene clusters of 22 pairs of chromosomes in sheep.Using CLUSTALW to construct a phylogenetic tree of olfactory receptor genes,17 families were classified,including 3 CLASS I and 14 CLASS II families,and further divided into 305 subfamilies.The orthologous analysis revealed that the sheep OR functional gene was distributed in 515 common orthologous groups(OGG)and obtained 28 sheep-specific OR genes,37 single-copy orthologous genes.2.Olfactory epithelium transcriptome detection showed 706 OR gene expression,the expression level was low,and FPKM was mostly between 1-10.There are 3,1,4,and 4 OR genes expressed in brain,muscle,fat,and olfactory bulb tissues respectively and FPKM is between 0.1 and 1.3.Assembled 1015 olfactory epithelium OR gene transcripts,corresponding to 521 OR genes,of which 254 OR genes existed in 2 or more transcripts.The results of RT-PCR and sequencing of different transcripts showed that there were exon skipping and different start codon selection splicing methods of OR gene,and different splicing methods affected the coding region sequence.In summary,we obtained the sequence,classification,evolution and expression information of all OR genes in sheep,which will promote further study on the relationship between sheep OR gene with feeding,reproduction and other behaviors among different breeds and individuals.