Complete Chloroplast Genome Sequences of Five Ormosia Species: Molecular Structure, Comparative Analysis, and Phylogenetic Analysis

The genus Ormosia comprises approximately 130 species, which are found in tropical regions all over the world. The taxonomy and evolutionary history are still ambiguous due to the lack of a solid phylogeny at the species level. Due to the fast advancement of high-throughput sequencing technology, it is now possible to retrieve the full chloroplast (cp) genome sequence, providing a molecular basis for phylogenetic analysis. Five species of Ormosia were used in this work, and their whole cp genomes were sequenced. One circular, quadripartite-structured molecule, ranging from 169,797 to 173,946 base pairs in length, was present in all five Ormosia species. The cp genomes of the five newly sequenced Ormosia species were further compared with the published cp genomes of O. pinnata. Ten hypervariable regions (Pi > 0.025) were uncovered in the Ormosia chloroplast genomes, among which petN-psbM showed the highest Pi value. Phylogenetic analysis revealed that O. microphylla and O. olivacea clustered with strong support. O. balansae was resolved as a sister to O. pinnata, and they were further found to be sisters to the remaining 13 Ormosia species. The cp genes of O. elliptica showed a close relationship to O. hosiei, and O. semicastrata clustered with O. emarginata. Taken together, the comprehensive analysis of the complete cp genomes of five Ormosia species offers valuable insight and information for reconstructing their phylogeny and sheds light on the evolutionary dynamics of the chloroplast genome in Ormosia.