Abstract
In the present study, the mitogenome of Tuber calosporum was assembled and analyzed. The mitogenome of T. calosporum comprises 15 conserved protein-coding genes, two rRNA genes, and 14 tRNAs, with a total size of 287,403 bp. Fifty-eight introns with 170 intronic open reading frames were detected in the T. calosporum mitogenome. The intronic region occupied 69.41% of the T. calosporum mitogenome, which contributed to the T. calosporum mitogenome significantly expand relative to most fungal species. Comparative mitogenomic analysis revealed large-scale gene rearrangements occurred in the mitogenome of T. calosporum, involving gene relocations and position exchanges. The mitogenome of T. calosporum was found to have lost several tRNA genes encoding for cysteine, aspartate, histidine, etc. In addition, a pair of fragments with a total length of 32.91 kb in both the nuclear and mitochondrial genomes of T. calosporum was detected, indicating possible gene transfer events. A total of 12.83% intragenomic duplications were detected in the T. calosporum mitogenome. Phylogenetic analysis based on mitochondrial gene datasets obtained well-supported tree topologies, indicating that mitochondrial genes could be reliable molecular markers for phylogenetic analyses of Ascomycota. This study served as the first report on mitogenome in the family Tuberaceae, thereby laying the groundwork for our understanding of the evolution, phylogeny, and population genetics of these important ectomycorrhizal fungi.
Highlights
The Tuber genus is a diversified lineage of truffle-forming fungi that produce hypogeous fruiting bodies
We detected two pairs of overlapping open reading frames (ORFs) in the mitogenome of T. calosporum, one of which located across the neighboring genes orf228 and orf211 (−10 bp) and the other of which was located between orf62 and orf84 (−28 bp) (Supplementary Table 1)
Comparative mitogenomic analysis indicated that intron gain was the primary factor that contributed to the size expansion of the T. calosporum mitogenome
Summary
The Tuber genus is a diversified lineage of truffle-forming fungi that produce hypogeous fruiting bodies. Tuber species must form ectomycorrhiza with their host plants to complete their life cycles. Plants provide carbon sources for truffles to grow and reproduce. The formation of this symbiotic relationship in nature plays an important role in maintaining the balance of forest ecosystem and promoting the carbon natural cycle (Franco et al, 2014; Corrales et al, 2018). Expecially T. melanosporum, has been used as model species to study the evolution, genetics, and ecological adaptation of ectomycorrhizal fungi (Martin et al, 2010; Murat et al, 2018b; Zarivi et al, 2018). Phylogenetic analysis found that the T. calosporum belonged to the Macrosporum group (Wan et al, 2016)
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