Complete chloroplast genome of Sabia discolor Dunn and comparative analysis with related species from Sabiaceae

Sabia discolor Dunn is an ethnomedicinally significant plant with underexplored genetic resources. To elucidate its chloroplast genome structure, evolutionary characteristics, and phylogenetic position within the genus Sabia, we sequenced and analyzed its complete chloroplast genome.

Using Illumina HiSeq™ platform for sequencing, followed by assembly with GetOrganelle and annotation with CPGAVAS2, we characterized the genome. The results showed that the chloroplast genome of S. discolor is a 161,581 bp circular DNA molecule with a typical quadripartite structure and a GC content of 39.25%. It harbors 129 genes, including 84 protein-coding genes, 8 rRNAs, and 37 tRNAs. We detected 80 simple sequence repeats (SSRs) and 55 long repeats. Codon usage bias analysis revealed a weak preference, with an effective number of codons (ENC) value of 49.01, primarily shaped by natural selection rather than mutation pressure. Comparative analysis identified a significant contraction in the inverted repeat (IR) regions and six highly variable regions (e.g., trnH-psbA, ndhF), which are proposed as potential molecular markers for species identification. Phylogenetic analysis based on complete chloroplast genomes revealed two major clades within Sabia, with S. discolor placed in Clade I, closely clustered with S. parviflora, S. limoniacea, S. fasciculata, and S. swinhoei, while S. dielsii formed a distinct basal lineage.

This study provides fundamental genetic resources for future research on the conservation, phylogenetics, and molecular identification of S. discolor and its relatives.