Phylogenetics Study to Compare Chloroplast Genomes in Four Magnoliaceae Species

Abstract

Magnoliaceae, a family of perennial woody plants, contains several endangered species whose taxonomic status remains ambiguous. The study of chloroplast genome information can help in the protection of Magnoliaceae plants and confirmation of their phylogenetic relationships. In this study, the chloroplast genomes were sequenced, assembled, and annotated in Woonyoungia septentrionalis and three Michelia species (Michelia champaca, Michelia figo, and Michelia macclurei). Comparative analyses of genomic characteristics, repetitive sequences, and sequence differences were performed among the four Magnoliaceae plants, and phylogenetic relationships were constructed with twenty different magnolia species. The length of the chloroplast genomes varied among the four studied species ranging from 159,838 bp (Woonyoungia septentrionalis) to 160,127 bp (Michelia macclurei). Four distinct hotspot regions were identified based on nucleotide polymorphism analysis. They were petA-psbJ, psbJ-psbE, ndhD-ndhE, and rps15-ycf1. These gene fragments may be developed and utilized as new molecular marker primers. By using Liriodendron tulipifera and Liriodendron chinense as outgroups reference, a phylogenetic tree of the four Magnoliaceae species and eighteen other Magnoliaceae species was constructed with the method of Shared Coding Sequences (CDS). Results showed that the endangered species, W. septentrionalis, is relatively genetically distinct from the other three species, indicating the different phylogenetic processes among Magnoliaceae plants. Therefore, further genetic information is required to determine the relationships within Magnoliaceae. Overall, complete chloroplast genome sequences for four Magnoliaceae species reported in this paper have shed more light on phylogenetic relationships within the botanical group.