Preliminary Analysis On The Transcriptome Of Skin Tissue With Different Coat Colors Of Chinese Domestic Donkey And Its Formation Causes

The color of the coat is an important basis for identifying domestic donkey breeds and also a characteristic of the biodiversity of domestic donkeys.In order to provide a theoretical basis for further research on genetic diversity of coat colors of Chinese domestic donkey,the regulatory mechanism of different coat colors of Chinese domestic donkey was studied at the tissue and molecular levels.In this study,relevant research was carried out to explore the correlation between different hair colors of Chinese domestic donkey and different hair colors of the same individual,and the following conclusions were drawn:1.Microscopic examination of the coat of Chinese domestic donkeys with different coat colors revealed that the black coat(including the back coat of aconite,black three powder,and black coat of green three powder)had dense black particles under the microscope,which basically covered the entire coat shaft;The white coat(including black three pink belly coat,green three pink white coat,white,and albino)and yellow coat are relatively sparse and loose in black particles seen under a microscope,forming some blank areas in the coat shaft.Some coats have almost no black particle distribution at the coat tips and are transparent.The above results indicate that the color of the coat is related to the distribution and content of black particles.The higher the content and density of black particles,the darker the color of the coat;The lower the content and dispersed distribution of black particles,the lighter the color of the coat.2.It was found that the content of total melanin in the dark coat of Chinese domestic donkeys with different colors was significantly higher than that in the light coat;The content of true melanin(except for white coat)in dark coat is significantly higher than that in light coat;The content of brown melanin(except for green coat)in dark coat is significantly higher than that in light coat.This indicates that the depth of the coat color of Chinese domestic donkeys is positively correlated with the total melanin content,and the difference in total melanin content of Chinese domestic donkeys is the key to the change in their coat color.3.Using RNA-Seq technology,we sequenced the transcriptome of the skin tissue of the same Chinese donkey with different coat colors(black and white).After screening and comparative analysis of the sequencing results of the two groups,we found 1165 differentially expressed genes,of which 756 genes were significantly upregulated and 409 genes were significantly down-regulated in the back black coat skin tissue.The data obtained from transcriptome sequencing were analyzed for GO function enrichment and KEGG signal pathway enrichment.The most significant three functional parts enriched were G-protein coupled receptor signal pathway,cytoskeleton part and signal receptor activator;The most significant signaling pathway is the hematopoietic cell lineage signaling pathway.Due to experimental needs,the melanin synthesis pathway was chosen as the key research signal pathway.The screened differential genes include TYR,TYRP1,TYRP2,MC1 R,ASIP,KIT,etc.4.Polymorphic loci of the following genes were screened from 14 Chinese domestic donkey populations with different coat colors:(1)A→G mutation occurred at the 259th base of the first exon of the TYR gene,which is a non synonymous mutation that causes the amino acid to change from isoleucine to valine.As the distribution of black coat in Chinese domestic donkeys decreases,the frequency of AA genotype gradually decreases,while the frequency of GG genotype gradually increases.This locus is related to the formation of black and white coat in Chinese domestic donkeys.(2)A polymorphic locus g.1702A→G was found on the second intron of the TYRP1 gene.The distribution of gene frequency and genotype frequency was different in Chinese domestic donkeys with different coat colors,with allele A being the dominant gene.The AA genotype had the highest frequency in gray three powders,the lowest frequency in aconite,and the GG genotype had the lowest frequency in black three powders.This indicates that the mutation locus g.1702A→G is related to the different coat colors of Chinese domestic donkeys.