Assembly and comparative analysis of the complete mitochondrial genomes of five Thaxterogaster species (Cortinariaceae, Basidiomycota): Insights into mitochondrial genome evolution and intrageneric phylogenetic relationships
The generic circumscription and taxonomic rank of Thaxterogaster have undergone substantial revisions over time, yet the intrageneric phylogenetic affinities of this genus remain contentious. While mitochondrial genomes are effective molecular markers for phylogenetic analyses, systematic studies based on complete mitogenomes of this genus are still lacking. In this study, we assembled and annotated the complete mitogenomes of five Thaxterogaster species and performed comparative genomic and phylogenetic analyses. The five mitogenomes are all circular molecules, ranging from 35,902 to 106,732 bp in length, with GC contents of 24.35%–29.15%. All mitogenomes shared a conserved repertoire of 15 core protein-coding genes, two rRNA genes, and 25–26 tRNA genes. The core gene complement and gene order are relatively conserved among the five species, whilst genome size, intron load, repeat sequence composition, and local syntenic architecture vary markedly. Phylogenetic analyses based on the mitochondrial core genes of 51 species revealed that the five Thaxterogaster species formed a well-supported distinct clade within Cortinariaceae , closely related to the clade comprising Hymenogastraceae and Strophariaceae . Collectively, our findings enhance the understanding of mitogenomic structural and evolutionary features in Thaxterogaster and provide a useful reference for future studies into mitogenome evolution in Cortinariaceae and allied taxa.