Intraspecific comparison of mitochondrial genomes in the entomopathogenic fungus Beauveria bassiana

Abstract:

[Objective] To understand the intraspecific genetic differentiation of mitochondrial genomes (mitogenomes) in Beauveria bassiana.[Methods] Mitogenomes of six isolates of B. bassiana were downloaded from GenBank. Composition and structure of these mitogenomes, nucleotide variations at exonic, intronic and intergenic regions were compared. Phylogenetic relationship of these isolates was analyzed based on common core protein-coding genes.[Results] The mitogenome size of different isolates of B. bassiana ranged from 28.8 to 32.3 kb. There were 14 common core protein-coding genes, 2 rRNA genes and 25 tRNA genes in all of these mitogenomes, showing a strong collinear relationship. However, the number of introns in different isolates varied (2 to 5 introns per isolate). Intron insertion/deletion polymorphism was found in cox1, cox2 and nad1, as the main factor contributing to variations of mitogenome size. Based on nucleotide variations at exonic, intronic and intergenic regions, the relative variability at intronic and intergenic regions was larger than that at exonic regions. Phylogenetic analysis revealed that these isolates of B. bassiana grouped together with a high support value, and isolates with identical intron distribution tended to cluster closely.[Conclusion] B. bassiana shows genetic differentiation in its mitogenome due to intron number variations, indel and single nucleotide polymorphism. Our data provide new evidence for understanding the differentiation of mitogenomes in fungal species.