Exploring the Mitochondrial Genomes of Phoebe Species (Lauraceae): Structural Dynamics and Functional Conservation

Plant mitochondrial genomes (mitogenomes) vary markedly in size and architecture despite generally slow rates of sequence evolution. Phoebe is an ecologically and economically valuable genus of Lauraceae, yet its mitogenome diversity remains poorly characterized. In this study, we newly sequenced, assembled, and annotated the mitogenomes of three nationally protected Class II wild plants (P. bournei, P. chekiangensis, P. zhennan) from China and compared their mitogenomic characteristics. The three assemblies were resolved into representative circular configurations ranging from 808 to 864 kb, with similar GC contents and conserved protein-coding capacity. Each mitogenome contained distinct 41 protein-coding genes, 27-28 transfer RNAs, and three ribosomal RNAs. Synteny analysis revealed extensive changes in homologous-block order and orientation despite substantial sequence homology among the three species. Abundant repeats occurred predominantly in noncoding regions, while plastid-derived fragments documented historical intracellular DNA transfer. The three species exhibited similar codon usage and predicted RNA-editing patterns, whereas low synonymous divergence limited inference from pairwise ratios. Phylogenetic analysis based on mitochondrial protein-coding genes recovered Phoebe as a well-supported monophyletic lineage. These results reveal substantial structural divergence accompanied by conserved nucleotide composition and coding capacity, providing valuable data for further understanding the evolutionary variation of plant mitogenomes of Phoebe and the Lauraceae.