The Taihangia mitogenome provides new insights into its adaptation and organelle genome evolution in Rosaceae

We present the first Taihangia mitogenome, uncovering frequent rearrangements and significant length variation in Rosaceae, likely driven by hybridization and repeat content, alongside widespread mito-chloroplast phylogenetic conflicts. Taihangia, an ancient and endangered monotypic genus within the subfamily Rosoideae of the family Rosaceae, is endemic to cliffs and serves as an ideal material for studying the adaptations of cliff-dwelling plants and the evolutionary processes of the Rosaceae family. In this study, the mitogenome and plastome of T. rupestris var. ciliata were assembled, with lengths of 265,633 bp and 155,467 bp, both exhibiting typical circular structures. Positive selection was detected in the nad4L and sdh4 genes, likely playing a role in adaptation to harsh environments. Comparative genomic analysis indicated that repetitive sequences are likely the main contributors to genome size variation in Rosaceae and also influence horizontal gene transfer between organelle genomes. In T. rupestris var. ciliata, 20 mitochondrial plastid DNA sequences were identified, including 16 complete plastid genes. Moreover, frequent rearrangements were observed in the non-coding regions of mitogenome within the subfamily Rosoideae, potentially linked to the complex evolutionary history and the presence of repetitive sequences. In contrast, coding regions remained highly conserved (over 83% similarity) to maintain essential mitochondrial functions. Phylogenomic analysis of the two organelle genomes revealed conflicts in the phylogenetic relationships within Rosaceae, potentially due to the inconsistent mutation rates and frequent hybridization events in the evolutionary history of the family. In conclusion, the organelle genome analysis of Taihangia provides crucial genomic resources for understanding the evolution and adaptation of Rosaceae species.