New Insights Into The Evolution of Chloroplast Genomes in Ochna Species (Ochnaceae, Malpighiales)

Ochnaceae DC. includes more than 600 species that exhibit potential values for environmental ecology, ornamental, pharmaceutical, and timber industries. Although studies on phylogeny and phytochemicals have been intensively conducted, chloroplast genome data of Ochnaceae species have not been fully explored. In this study, the next-generation sequencing method was used to sequence the chloroplast genomes of Ochna integerrima and Ochna serrulata which were 157 329 and 157 835 bp in length, respectively. These chloroplast genomes had a quadripartite structure and contained 78 protein-coding genes, 30 tRNAs, and 4 rRNAs. Comparative analysis revealed 8 hypervariable regions, including trnK_UUU-trnQ_UUG, rpoB-psbM, trnS_GGA-rps4, accD-psaI, rpl33-rps18, rpl14-rpl16, ndhF-trnL_UAG, and rps15-ycf1 among 6 Ochnaceae taxa. Additionally, there were shared and unique repeats among 6 examined chloroplast genomes. The notable changes were the loss of rpl32 in Ochna species and the deletion of rps16 exon 2 in O. integerrima compared to other taxa. This study is the first comprehensive comparative genomic analysis of complete chloroplast genomes of Ochna species and related taxa in Ochnaceae. Consequently, the current study provides initial results for further research on genomic evolution, population genetics, and developing molecular markers in Ochnaceae and related taxa.