Sequencing And Analysis Of The Mitochondrial Genome Of Metarhizium Robertsii

Mitochondrial genome has been widely applied to the biological study of genetic structure and system classification because of its rapid evolution and strict adherence to maternal inheritance.It is an effective tool for studying the evolution of fungal systems and genetic relationships.Metarhizium,which is commonly used as an entomopathogenic fungus.The current mitochondrial genome data of Metarhizium is not perfect.In order to further improve the mitochondrial genomic data of Metarhizium and to further the theoretical research on the genetics and evolution of insect pathogenic fungi,we selected Metarhizium robertsii ARSEF 2575 in this paper,used PDA solid medium culture and CTAB method to extract total DNA.Then we got complete mitochondrial genome of M.Robertsii by high throughput sequencing,PCR amplification,Sanger sequencing,and assembly and annotation it.The mitochondrial genome was compared with the data on the existing fungi belonging to the Clavicipitaceae on the NCBI.Combined with 17 common protein encoding genes of 17 species of Hypocreales,their phylogenetic relationships were reconstructed.The result is as follows:The complete mitochondrial genome size of M.Robertsii is 24945 bp.It contains 14 common protein-coding genes,2 ribosomal RNA genes,and 25 transfer RNA genes.The type and arrangement of protein-coding genes of the fungi are basically similar to Clavicipitaceae.In addition,similar to most fungi,the protein coding genes,tRNA genes,and ribosomal RNA genes of the mitochondrial genome of M.Robertsii has more obvious A+T bias.By analyzing the composition of the 3 bases of the codons encoding the protein-coding genes,it was found that in the codons,the A and T contents at the first position differed little,while the T content at the second position was significantly doubled higher than that at the A,the A content of the 3rd site was the highest among the three sites,and the total A+T ratio reached 83.4%.The 14 protein-coding genes were all initiated with ATG and ended with TAA,and no other start or stop codons were found.In the amino acid composition of M.Robertsii,leucine was used most frequently,followed by isoleucine,phenylalanine and serine,which together accounted for 42.93% of the total mitochondrial amino acids.We choose the published Hypocreales fungus in NCBI and M.Robertsii,based on the amino acid sequences of the 14 protein-coding genes,made phylogenetic analysis by using the maximum likelihood method.The resulting topological structure is similar to the current classification of Hypocreales species,showing that Metarhizium robertsii has the closest relationship with Metarhizium anisopliae.Comparing the mitochondrial genome of Clavicipitaceae,we found that there were differences in the number,size,and overlap of seven fungal species in the intergenic region and gene region.In this study,the complete mitochondrial genome of M.Robertsii was determined,spliced,annotated and analyzed.The structure and characteristics of the genome were described.The mitochondrial genomes of the seven species of the genus Clavicipitaceae were reported and compared to establish phylogenetic relationships tree.Enriched mitochondrial genomic data of ericaceae fungus provides some references for the further development of phytopathogenic fungi.