The complete chloroplast genome sequence of Heteropolygonatum ginfushanicum (Asparagaceae) and phylogenetic analysis

Complete chloroplast genome sequencing and comparative analysis of threatened dragon trees Dracaena serrulata and Dracaena cinnabari

Dracaena (Asparagaceae family) tree is famous for producing "dragon blood"—a bioactive red-colored resin. Despite its long history of use in traditional medicine, little knowledge exists on the genomic architecture, phylogenetic position, or evolution. Hence, in this study, we sequenced the whole chloroplast (cp) genomes of D. serrulata and D. cinnabari and performed comparative genomics of nine genomes of the genus Dracaena. The results showed that the genome sizes range from 155,055 (D. elliptica) to 155,449 (D. cochinchinensis). The cp genomes of D. serrulata and D. cinnabari encode 131 genes, each including 85 and 84 protein-coding genes, respectively. However, the D. hokouensis had the highest number of genes (133), with 85 protein coding genes. Similarly, about 80 and 82 repeats were identified in the cp genomes of D. serrulata and D. cinnabari, respectively, while the highest repeats (103) were detected in the cp genome of D. terniflora. The number of simple sequence repeats (SSRs) was 176 and 159 in D. serrulata and D. cinnabari cp genomes, respectively. Furthermore, the comparative analysis of complete cp genomes revealed high sequence similarity. However, some sequence divergences were observed in accD, matK, rpl16, rpoC2, and ycf1 genes and some intergenic spacers. The phylogenomic analysis revealed that D. serrulata and D. cinnabari form a monophyletic clade, sister to the remaining Dracaena species sampled in this study, with high bootstrap values. In conclusion, this study provides valuable genetic information for studying the evolutionary relationships and population genetics of Dracaena, which is threatened in its conservation status.

Characterization of the Complete Chloroplast Genome Sequence of the Socotra Dragon`s Blood Tree (Dracaena cinnabari Balf.)

The Socotra dragon`s blood tree (Dracaena cinnabari Balf.) is endemic to the island of Socotra in Yemen. This iconic species plays an essential role in the survival of associated organisms, acting as an umbrella tree. Overexploitation, overgrazing by livestock, global climate change, and insufficient regeneration mean that the populations of this valuable species are declining in the wild. Although there are many studies on the morphology, anatomy, and physiology of D. cinnabari, no genomic analysis of this endangered species has been performed so far. Therefore, the main aim of this study was to characterize the complete chloroplast sequence genome of D. cinnabari for conservation purposes. The D. cinnabari chloroplast genome is 155,371 bp with a total GC content of 37.5%. It has a quadripartite plastid genome structure composed of one large single-copy region of 83,870 bp, one small single-copy region of 18,471 bp, and two inverted repeat regions of 26,515 bp each. One hundred and thirty-two genes were annotated, 86 of which are protein-coding genes, 38 are transfer RNAs, and eight are ribosomal RNAs. Forty simple sequence repeats have also been identified in this chloroplast genome. Comparative analysis of complete sequences of D. cinnabari chloroplast genomes with other species of the genus Dracaena showed a very high conservativeness of their structure and organization. Phylogenetic inference showed that D. cinnabari is much closer to D. draco, D. cochinchinensis, and D. cambodiana than to D. terniflora, D. angustifolia, D. hokouensis, and D. elliptica. The results obtained in this study provide new and valuable omics data for further phylogenetic studies of the genus Dracaena as well as enable the protection of genetic resources of highly endangered D. cinnabari.