Study On The Evolution Of Five Primates Bitter Taste Receptor Genes

Foraging is the most important and basic activity in the survival of animals,and is the source of all the nutrients and energy needed for animal growth,reproduction,and exercise.Taste is the basis of animal foraging.Taste refers to the sensation triggered by the taste buds on the surface of the tongue.It can feel the sweet,salty,sour,bitter and umami taste,which is closely related to the animal's diet and external environment.Among these five tastes,bitterness is especially important,because many toxic substances are often bitter,and bitterness perception can help animals detect and avoid toxins in food,so bitterness plays an important role in the survival of animals,especially for plants.Primates,which are mainly dietary,are particularly important because there are a lot of bitter substances in plant tissues.Therefore,the study of primate bitter taste receptor genes is of great significance for understanding their living environment and food choices.At present,the research on the bitter taste receptor gene focuses on the adaptive evolution and functional analysis of the vertebrate bitter taste receptor gene in different dietary species.The research on primate bitter taste receptor genes is mainly focused on humans,and there are few studies on other primates.In this study,the bitter receptor(T2R)genes of white-headed langurs(Trachypithecus leucocephalus),Francois langur(Trachypithecus francoisi),douc langur(Pygathrix nemaeus)of the Colobus monkey subfamily(Colobinae)and macaques(Macaca mulatta)and assam macaque(Macaca assamensis)of the macaque subfamily(Cercopithecinae)were amplified and sequenced by PCR amplification and gene cloning techniques.Use bioinformatics methods and literature search methods to search and identify other primates T2R genes.The molecular phylogenetic tree was constructed by neighbor joining(NJ)and maximum likelihood(ML)methods,with the zebrafish V1 r gene as the outgroup.Phylogenetic independent comparison(PIC),analysis of variance(ANOVA)test,independent sample t test were used to analyze the relationship between primate T2R gene number and diet.The main results are as follows:1.In this study,142 T2R genes were successfully amplified from 5 primates,including 129 intact genes,1 partial gene,and 12 pseudogenes.Specifically,there are 25 intact genes and 3 pseudogenes in white-headed langurs,24 intact genes and 2 pseudogenes in Francois langur,24 intact genes,1 partial gene and 3 pseudogenes in douc langur,28 intact genes and 2 pseudogenes in macaque,28 intact genes and 2 pseudogenes in Assamese macaque.The results showed that the number of intact T2R genes was different in different subfamilies,and the number of intact genes in the macaque subfamily was greater than that of the colobus monkey subfamily.The intact T2R gene sequence length is between 876 bp and 1017 bp,and the amino acid sequence has a seven-time transmembrane structure.2.By searching relevant literature and using bioinformatics methods to find the T2R gene in primates,combined with the five species amplified in this study,a total of 9 families of 37 primates T2R gene families were obtained.Except that the orangutan(Pongo pygmaeus)only found protein sequences,others found nucleotide sequences.Through sorting and analysis of the number of primate T2R genes,it was found that there are differences in the composition and number of T2R genes in different species.It refers to the largest number of T2R genes in aye-aye(Daubentonia madagascariensis),the largest number of intact T2R genes in ghost baboons(Mandrillus leucophaeus),and the highest proportion of T2R pseudogenes in bamboo lemurs(Prolemur simus).3.Phylogenetic analysis was performed based on the intact T2R gene sequences of 36 primates,The results showed that the orthologous bitter taste receptor genes of Francois langur and white-headed langurs always clustered in the same branch.The blue-eyed black lemurs(Eulemur flavifrons)and the black beauty lemurs(Eulemur macaco)are always clustered together,and other primate orthologous bitter receptor genes are also mostly clustered together,indicates that the bitter taste receptor gene is relatively conserved in primates.4.Based on the correlation analysis of 37 primates T2R gene numbers and diet,the results showed: 1)PIC analysis showed that there was no significant positive correlation between primate total T2R gene numbers and diet(R=-0.013,P=0.462>0.05),The number of potential functional T2R genes was also not significantly positively correlated with diet(R=0.052,P=0.093>0.05),while the number of intact T2R genes was significantly correlated with diet(R=0.119,P=0.021<0.05);2)The results of analysis of variance showed that the mean number of intact T2R genes of bitter taste receptor genes of different dietary primates had a significant difference(P=0.001<0.05);3)Independent sample t test(non-parametric)results show that the difference in the mean value of the intact T2R genes of fruit-eating and leaf-eating primates has no significant correlation(P>0.05).The above results indicate that diet can affect the evolution of primates T2R genes.5.Selection pressure analysis showed that the primates T2R1,T2R4,T2R7,T2R16,and T2R38 genes underwent positive selection,and there were more positive selection sites in functional regions.These positive selection sites were mainly located in the extracellular region(EL)and Transmembrane region(TM),especially concentrated in EL3 and TM2;high degree of extracellular differentiation,combined with taste substances,transmembrane region is mainly to modify the encoded protein,from the distribution of positive selection sites,The pressure of T2R gene selection evolution mainly comes from the recognition and binding of bitter substances and the modification of proteins,which in turn helps primates reduce the intake of bitter substances.