Next-Generation Genome Sequencing of Sheds Light on the Structural Evolution of Plastid rRNA Operon and Phylogenetic Implications within Saxifragales.

The genus , with about 470 recognized species, is classified in the family Crassulaceae of the order Saxifragales. Phylogenetic relationships within the Saxifragales are still unresolved and controversial. In this study, the plastome of was firstly presented, with a focus on the structural analysis of operon and phylogenetic implications within the order Saxifragaceae. The assembled complete plastome of is 149,397 bp in size, with a typical circular, double-stranded, and quadripartite structure of angiosperms. It contains 133 genes, including 85 protein-coding genes (PCGs), 36 tRNA genes, 8 rRNA genes, and four pseudogenes (one , one , and two ). The predicted secondary structure of 16S rRNA includes three main domains organized in 74 helices. Further, our results confirm that 4.5S rRNA of higher plants is associated with fragmentation of 23S rRNA progenitor. Notably, we also found the sequence of putative promoter has some evolutionary implications within the order Saxifragales. Moreover, our phylogenetic analyses suggested that had a closer relationship with than , and supported the taxonomic revision of . Our findings of the present study will be useful for further investigation of the evolution of plastid rRNA operon and phylogenetic relationships within Saxifragales.