Study On Population History And System Evolution Of Giant Panda Baylisascaris Schroederi

Baylisascaris schroederi is one of the main parasites infecting giant pandas,and has become one of the main causes of abnormal death of giant pandas in recent decades.Through the sequencing and analysis of the mitochondrial genome,ribosomal genome and whole genome of the giant panda Baylisascaris schroederi,its classification and differentiation status can be studied in depth and systematically,and the related scientific issues of Baylisascaris schroederi can be revealed at the molecular level.It is beneficial to reduce the harm of Baylisascaris schroederi to giant pandas,and has positive and practical significance for the protection of giant panda populations.This study intends to use the homologous gene analysis of the whole genome sequence,the mitochondrial cytb gene sequence and the ribosomal 18 S gene sequence to carry out a phylogenetic analysis of the Baylisascaris schroederi.The research results are as follows:1.In this study,at the genome-wide level,the giant panda Baylisascaris schroederi was compared with five species of nematodes(including three species,Ascaris suum,Parascaris univalens,Toxocara canis and one free-living nematode,Caenorhabditis elegans;a plantparasitic nematode,Meloidogyne hapla),and the whole genome was compared and analyzed.The study found that the divergence time between the four Ascaris species was about 25.5-160 million years ago,and among the four Ascaris species,Toxocara canis was first differentiated about 159 million years ago.The results showed that the relationship between Baylisascaris schroederi and Parascaris univalens was the closest,and the relationship with Ascaris suum was the second,and their differentiation time was between 25.5-44.7 million years ago;Toxocara canis is the most distantly related;2.In this study,the complete mitochondrial genome of Baylisascaris schroederi was successfully assembled by blast alignment using the third-generation Pacbio sequencing data,and the phylogenetic tree and molecular clock of 13 species of nematodes from three genera were constructed using the mitochondrial cytb gene sequence,obtained the results consistent with the whole genome sequence analysis,that is,the relationship between the Baylisascaris schroederi and Parascaris univalens is the closest,the relationship with Ascaris suum is the second,and the relationship with Toxocara canis is the farthest.3.In this study,by aligning the 29-segment the ribosomal 18 S gene sequences of 4 genera of roundworms,and using BEAST software to construct the ribosomal 18 S gene sequence molecular clock and phylogenetic tree,it was found that the Baylisascaris schroederi has the closest genetic relationship with roundworms of Baylisascaris.Toxocara canis species is the most distantly related;Through phylogenetic analysis,this study systematically analyzed the taxonomic status and differentiation time of Baylisascaris schroederi in the order Ascaridina and nematodes.