Apostasia Mitochondrial Genome Analysis and Monocot Mitochondria Phylogenomics

Apostasia shenzhenica belongs to the subfamily Apostasioideae and is a primitive group located at the base of the Orchidaceae phylogenetic tree. However, the A. shenzhenica mitochondrial genome (mitogenome) is still unexplored, and the phylogenetic relationships between monocots mitogenomes remain unexplored. In this study, we discussed the genetic diversity of A. shenzhenica and the phylogenetic relationships within its monocotyledon mitogenome. We sequenced and assembled the complete mitogenome of A. shenzhenica, resulting in a circular mitochondrial draft of 672,872 bp, with an average read coverage of 122× and a GC content of 44.4%. A. shenzhenica mitogenome contained 36 protein-coding genes, 16 tRNAs, two rRNAs, and two copies of nad4L. Repeat sequence analysis revealed a large number of medium and small repeats, accounting for 1.28% of the mitogenome sequence. Selection pressure analysis indicated high mitogenome conservation in related species. RNA editing identified 416 sites in the protein-coding region. Furthermore, we found 44 chloroplast genomic DNA fragments that were transferred from the chloroplast to the mitogenome of A. shenzhenica, with five plastid-derived genes remaining intact in the mitogenome. Finally, the phylogenetic analysis of the mitogenomes from A. shenzhenica and 28 other monocots showed that the evolution and classification of most monocots were well determined. These findings enrich the genetic resources of orchids and provide valuable information on the taxonomic classification and molecular evolution of monocots.