Decoding the chloroplast genomes of five Iranian Salvia species: insights into genomic structure, phylogenetic relationships, and molecular marker development.

BACKGROUND

The genus Salvia, a prominent member of the Lamiaceae family, is renowned for its ecological, medicinal, and economic significance. Despite its importance, molecular data, particularly chloroplast (cp.) genome information, remain scarce for many native Iranian Salvia species. In this study, we sequenced and analyzed the complete cp. genomes of five Iranian Salvia species (S. aethiopis, S. sclarea, S. glutinosa, S. verticillata, and S. officinalis) to elucidate their genomic structure, evolutionary relationships, and potential for biotechnological applications.

RESULTS

The cp. genomes of the five Salvia species exhibited a conserved quadripartite structure, with sizes ranging from 151,163 to 151,662 bp, and a GC content of 38%. Each genome contained 132 or 131 genes, comprising 86 or 87 protein-coding, 8 rRNA, and 37 tRNA genes, with duplications in rpl2, rpl23, and rps12. Minor variations in gene content were observed, such as the absence of trnS-CGA in S. glutinosa. Comparative analysis of IR boundaries showed subtle expansions in S. officinalis and S. sclarea, while S. glutinosa remained stable. Trans-splicing of the rps12 gene was observed in all species, with complex structures in S. glutinosa and S. sclarea. Codon usage analysis revealed a preference for A/U-ending codons, with S. verticillata displaying unique patterns. Nucleotide diversity (Pi) identified highly variable regions, such as rpl14-rpl16 and psbK-psbI, as potential molecular markers. Phylogenetic analysis resolved distinct clades, with S. aethiopis and S. sclarea forming a close group, S. glutinosa clustering with S. chanryoenica, and S. officinalis showing genetic homogeneity with Mediterranean species. S. verticillata exhibited an earlier divergence, highlighting the genus's evolutionary complexity.

CONCLUSIONS

This study provides critical genomic resources for species identification, phylogenetic studies, and the development of molecular markers, facilitating the conservation of native Salvia species and their utilization in breeding programs for medicinal and aromatic traits.