Comparative Analysis of Chloroplast Genomes for the Genus Manglietia Blume (Magnoliaceae): Molecular Structure and Phylogenetic Evolution

Manglietia Blume, belonging to the Magnoliaceae family and mainly distributed in tropical and subtropical regions of Asia, has great scientific and economic value. In this study, we employed next-generation sequencing followed by de novo assembly to investigate the adaptive evolution of Manglietia using plastid genetic information. We newly sequenced the complete or nearly complete plastomes of four Manglietia species (Manglietia aromatica, Manglietia calcarea, Manglietia kwangtungensis, and Manglietia glauca) and conducted comparative analysis with seventeen published plastomes to examine the evolutionary pattern within this genus. The plastomes of these five newly sequenced Manglietia species range from 157,093 bp (M. calcarea2) to 160,493 bp (M. kwangtungensis), all exhibiting circular structures when mapped. Nucleotide diversity was observed across the plastomes, leading us to identify 13 mutational hotspot regions, comprising eight intergenic spacer regions and five gene regions. Our phylogenetic analyses based on 77 protein-coding genes generated phylogenetic relationships with high support and resolution for Manglietia. This genus can be divided into three clades, and the previously proposed infrageneric classifications are not supported by our studies. Furthermore, the close affinity between M. aromatica and M. calcarea is supported by the present work, and further studies are necessary to conclude the taxonomic treatment for the latter. These results provide resources for the comparative plastome, breeding, and plastid genetic engineering of Magnoliaceae and flowering plants.