Annotation Of The Mitochondrial Genome Of Tricholoma Bakamatsutake And Comparison With Related Species

Mitochondrial DNA(mtDNA)is independent of the nuclear genome for replication and transcription.It has extremely high specificity and uniqueness,and is also an important marker for classification and identification.As a substitute product of Tricholoma matsutake,Tricholoma bakamatsutake has attracted much attention.It is of great significance to develop and use this precious wild resource of Tricholoma bakamatsutake.So far,no mitochondrial genome of Tricholoma bakamatsutake has been reported.In this paper,a Tricholoma bakamatsutake strain from Liaoning was used as the research object.The mitochondrial genome was assembled by high-throughput sequencing and annotated.The genome sequences of Tricholoma matsutake,Laccaria amethystina,Laccaria bicolor and Desarmillaria tabescens published by NCBI were selected and compared with Tricholoma bakamatsutake,and phylogenetic analysis was performed according to standard protein coding genes.The total length of the Tricholoma bakamatsutake mitochondrial genome is 122565 bp.The genome contains two ribosomal RNAs(rnl and rns),29 transitRNAs(tRNA),14 standard protein coding genes(PCGs),one rps3,and 13 intergenic regions open reading frames(ORF).The mitochondrial genome of Tricholoma bakamatsutake is in line with the high AT content of the fungal mitochondrial genome,accounting for up to 78.5%.Most of the codons of the standard protein encoding gene PCGs start with ATG except cox1,which starts with GTG,and all of the 14 genes end with the stop codon TAA.Among the amino acid composition of the protein-encoding genes,the most frequently used is Leu,which has been used 2116 times,and the Ile,Lys,Phe,Ser and Asn are used frequently too.The above six amino acids accounted for 57.29% of the total amino acids.The mtDNA gene interval of Tricholoma matsutake is long,and there is no repeat of long fragments.It shows the characteristics of sequence degradation in genes rnl,cob,cox2 and nad4.Analysis and comparison of mitochondrial genome,gene sequence,PCGs codons,and independent ORFs were performed using four closely related species of Tricholoma bakamatsutake,namely Tricholoma matsutake,Laccaria amethystina,Laccaria bicolor,and Desarmillaria tabescens.We found that the situation of the mitochondrial genome amino acid usage of 5 related species is more consistent;among the genes encoding proteins in the mitochondrial genome,except for the cox1 gene of Tricholoma bakamatsutake and Tricholoma matsutake,GTG is used as the start codon,the nad2 gene of Tricholoma matsutake,and the atp9 gene of Desarmillaria tabescens are used TAG as the stop codon,and all the rest codons conform to the law of ATG as the start codon and TAA as the stop codon.Analysis of the basic sequence of the mitochondrial genome,intron insertion sites,and amino acid usage revealed that Tricholoma bakamatsutake and Tricholoma matsutake are closely related,and Laccaria amethystina is closer to Laccaria bicolor.Phylogenetic analysis further confirmed that the speculation about related species was true.It was also found that Tricholoma bakamatsutake and Tricholoma matsutake belonged to Tricholomaceae,Laccaria amethystina and Laccaria bicolor to Hydnanglaceae,and Desarmillaria tabescens to Physalacriaceae.In this study,the mitochondrial genome of Tricholoma bakamatsutake was analyzed and compared with the fungal mitochondrial genomes of closely-related fungi.Understanding the species of Tricholoma bakamatsutake provides data support for mitochondrial genome analysis and evolutionary research of Tricholomaceae,and further identifies the differences between Tricholoma bakamatsutake and Tricholoma matsutake.At the same time,this study relocates the classification of five closely related species and provides a theoretical basis for updating the classification of fungal species.