Mitochondrial Genomes from Fungal the Entomopathogenic Moelleriella Genus Reveals Evolutionary History, Intron
Chengjie Xiong1, Yongsheng Lin1, Nemat O Keyhani2
1State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, College of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou 350002, China.
Abstract:
Members of the genus Moelleriella (Hypocreales, Clavicipitaceae) are insect pathogens with specificity for scale insects and whiteflies. However, no mitochondrial genomes are available for these fungi. Here, we assembled seven mitogenomes from M. zhongdongii, M. libera, M. raciborskii, M. gracilispora, M. oxystoma, Moelleriella sp. CGMCC 3.18909, and Moelleriella sp. CGMCC 3.18913, which varied in size from 40.8 to 95.7 Kb. Synteny and codon usage bias was relatively conserved, with the mitochondrial gene arrangement being completely homologous to the gene order of 21 other species within the Hypocreales. Nevertheless, significant intron polymorphism was observed between Moelleriella species. Evolutionary analyses revealed that all 15 core protein-coding genes had ka/ks < 1, indicating purifying selection pressure. Sequence variation within the mitochondrial ATP synthase F0 subunit 6 (atp6) gene showed the largest genetic distance, with the ATP synthase F0 subunit 9 (atp9) gene showing the smallest. Comparative analyses of mitogenomes revealed that introns were the primary factor contributing to the size variation in Moelleriella and, more broadly, within Hypocreales mitogenomes. Phylogenetic analyses indicated that the seven Moelleriella species examined form a well-supported clade, most closely related to Metarhizium. These data present the first mitogenomes from Moelleriella and further advance research into the taxonomy, origin, evolution, and genomics of Moelleriella.
Insights
This study presents the first mitochondrial genomes for seven *Moelleriella* insect pathogens. Intron variations significantly influence fungal genome size and evolution, revealing a close relationship with *Metarhizium*.
Area of Science:
- Mycology
- Genomics
- Evolutionary Biology
Background:
- *Moelleriella* fungi are insect pathogens specific to scale insects and whiteflies.
- Mitochondrial genomes for *Moelleriella* species were previously unavailable, limiting genomic and evolutionary studies.
Purpose of the Study:
- To assemble and analyze the first seven mitochondrial genomes from the *Moelleriella* genus.
- To investigate genome size variation, gene content, codon usage, and evolutionary pressures within *Moelleriella*.
- To establish the phylogenetic position of *Moelleriella* within the Hypocreales order.
Main Methods:
- Sequencing and assembly of seven *Moelleriella* mitogenomes.
- Comparative genomic analyses of synteny, gene order, and codon usage.
- Analysis of intron polymorphism and sequence variation in protein-coding genes.
- Phylogenetic analyses using core protein-coding genes.
Main Results:
- Seven *Moelleriella* mitogenomes ranged from 40.8 to 95.7 Kb, with significant intron polymorphism contributing to size variation.
- Gene arrangement was conserved across Hypocreales, and purifying selection pressure (ka/ks < 1) was observed.
- The *atp6* gene showed the largest genetic distance, while *atp9* showed the smallest.
- Phylogenetic analyses placed the seven *Moelleriella* species in a well-supported clade, closely related to *Metarhizium*.
Conclusions:
- Mitochondrial genome size variation in *Moelleriella* and Hypocreales is primarily driven by introns.
- The study provides foundational genomic data for *Moelleriella*, advancing understanding of their taxonomy, evolution, and genomics.
- The findings establish *Moelleriella*'s phylogenetic relationship within the Clavicipitaceae family.
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