Comparative analysis of multi-chromosomal mitochondrial genome of Bletilla striata: homologous recombination mediated by repetitive sequences

BACKGROUND: Bletilla striata, a species within the genus Bletilla, holds significant medicinal and ornamental value. For further exploring the organelle of B. striata, the first complete mitochondrial genome (mitogenome) was assembled and annotated. RESULTS: The B. striata mitogenome exhibits a unique multi-chromosomal structure, spanning a total size of 746,435 bp, and contains 63 annotated genes, including 34 protein-coding genes (PCGs), 26 tRNA genes, and 3 rRNA genes. A total of 376 repetitive sequences were identified, with six pairs of repeats potentially meditating homologous recombination. Additionally, we detected 77 homologous segments in the chloroplast and mitochondrial genomes, among which 60 complete genes were further annotated. Phylogenetic analysis showed B. striata in close relation to the Apostasia genus, underscoring its evolutionary position within Orchidaceae. CONCLUSION: These findings shed light on the mitogenome structure and genetic characteristics of B. striata, offering a foundational framework for future explorations into its evolutionary dynamics.