Abstract
Platycrater arguta (Hydrangeaceae), a rare and endangered Tertiary relict shrub endemic to East Asia, holds significant ecological and evolutionary value. However, the P. arguta mitochondrial (mt) genome remains unexplored, limiting insights into its cytoplasmic evolution and phylogenetic relationships. In this study, a complete mt genome of P. arguta was sequenced, and we assembled the mt genome into two linear contigs for description, due to the complexity of its chromosome structure. The mt genome encodes 37 protein-coding genes, 27 tRNA genes, and three rRNA genes. A total of 687 RNA editing sites were predicted, and the most RNA editing sites were found in the nad4 gene. Repeat sequences with different sizes were detected in the mt genome, including 160 simple sequence repeats, 26 tandem repeats, and 320 dispersed repeats. Phylogenetic analysis grouped P. arguta with Hydrangea macrophylla (Hydrangeaceae), which is closely related to Eucommiaceae and Ericaceae. This study provides the first assembled and annotated mt genome of P. arguta, which enhances our understanding of the genome of this relict plant in Hydrangeaceae. Taken together, this study offered foundational data for conservation strategies, molecular breeding, and evolutionary studies of this endangered relict species.