Study On The Mechanism Of MGAM Gene In Adaptation To Starch Diet In Domestic Dogs

In the long history,the domestic dog（Canis lupus familiaris）has accompanied human beings for tens of thousands of years,and is one of the most trusted companions of human beings.The domestic dog is not only the first domesticated species,but also the only large predator to be domesticated.In the process of domestication from wolves to domestic dogs,the most important thing is the adaptation of domestic dogs to a high-starch diet.At present,it is known that in adapting to high starch diet environment,domestic dogs mainly increase enzyme activity to digest more starch by increasing the copy number of AMY2 B gene,but this mechanism does not exist in glycosylase-Glucoamylase（MGAM）gene,and MGAM gene further hydrolyzes sugars produced in starch and other sources of oligosaccharides to obtain more glucose,so that domestic dogs can better adapt to high starch diet,but there are few studies.This study is based on the MGAM gene to explore the genetic mechanism of diet adaptation in domestic dogs and wolves.In this study,the genomic data of 627 domestic dogs and 46 wolves were collected to form a genetic data set of 673 individuals.The MGAM gene was analyzed,and combined with the ATAC database of the small intestine of domestic dogs,Multiple high-frequency SNP sites were found in both domestic dog and Wolf populations.It was speculated that these sites may have promoter or enhancer activity,and these sites and surrounding fragments were inserted into PGL3-basic and PGL3-promoter vectors respectively.Two DNA fragments with promoter activity in MGAM gene were verified by fluorescence double report experiment,and then three SNP sites contained in these two promoter regions were further explored.It was found that the base change of chr16:7,215,916 site would affect the promoter activity,and the promoter activity of chr16:7,215,916 site C in dogs was higher than that in wolves when the chr16:7,215,916 site was T base.At the same time,through the prediction of Candidate transcription factors,we predicted that CTCF protein and TFAP2 A protein may be candidate transcription factors that interact with chr16:7,215,916 site and surrounding DNA fragments.These two Candidate transcription factors prefer the C allele at chr16:7,215,916.The promoter activity mediated by this site may change the expression pattern of MGAM gene in domestic dogs and wolves,This expression pattern may further promote the increase of MGAM gene expression and enhance the activity of MGAM disaccharidase in domestic dogs.This discovery may partly analyze the mechanism by which dogs can obtain more glucose from starch to adapt to high-starch diets,laying the foundation for the research on the adaptation of dogs to high-starch diets.At the same time,the verification of the two promoter fragments in the MGAM gene fills the gaps in the research on the transcriptional regulatory region of the MGAM gene in domestic dogs and wolves in the scientific community,and better reveals the domestication mechanism of domestic dogs.