No abstract

In this study, the mitogenome of Hannaella oryzae was sequenced by next-generation sequencing (NGS) and successfully assembled. The H. oryzae mitogenome comprised circular DNA molecules with a total size of 26,444 bp. We found that the mitogenome of H. oryzae partially deleted the tRNA gene transferring cysteine. Comparative mitogenomic analyses showed that intronic regions were the main factors contributing to the size variations of mitogenomes in Tremellales. Introns of the cox1 gene in Tremellales species were found to have undergone intron loss/gain events, and introns of the H. oryzae cox1 gene may have different origins. Gene arrangement analysis revealed that H. oryzae contained a unique gene order different from other Tremellales species. Phylogenetic analysis based on a combined mitochondrial gene set resulted in identical and well-supported topologies, wherein H. oryzae was closely related to Tremella fuciformis. This study represents the first report of mitogenome for the Hannaella genus, which will allow further study of the population genetics, taxonomy, and evolutionary biology of this important phylloplane yeast and other related species.

The genus of Tricholoma is a group of important ectomycorrhizal fungi. The overlapping of morphological characteristics often leads to the confusion of Tricholoma species classification. In this study, the mitogenomes of five Tricholoma species were sequenced based on the next-generation sequencing technology, including T. matsutake SCYJ1, T. bakamatsutake, T. terreum, T. flavovirens, and T. saponaceum. These five mitogenomes were all composed of circular DNA molecules, with sizes ranging from 49,480 to 103,090 bp. Intergenic sequences were considered to be the main factor contributing to size variations of Tricholoma mitogenomes. Comparative mitogenomic analysis showed that the introns of the Agaricales mitogenome experienced frequent loss/gain events. In addition, potential gene transfer was detected between the mitochondrial and nuclear genomes of the five species of Tricholoma. Evolutionary analysis showed that the rps3 gene of the Tricholoma species was under positive selection or relaxed selection in the evolutionary process. In addition, large-scale gene rearrangements were detected between some Tricholoma species. Phylogenetic analysis using the Bayesian inference and maximum likelihood methods based on a combined mitochondrial gene set yielded identical and well-supported tree topologies. This study promoted the understanding of the genetics, evolution, and phylogeny of the Tricholoma genus and related species.