Molecular characteristics and phylogenetic definition on the complete chloroplast genome of Petrocodon longitubus

Petrocodon is a small genus in the family Gesneriaceae, which is special for its remarkable floral diversity, and has high ornamental value. In this study, the complete chloroplast genome sequence and genome characteristics of Petrocodon longitubus are first reported. The genome size is 152,958 bp, including a large single-copy region (LSC, 83,901 bp), a small single-copy region (SSC, 18,255 bp), and two inverted repeat sequences (IRs, 25,401 bp, each). The chloroplast genome of P. longitubus was analyzed, revealing a total GC content of 37.47%. A total of 131 genes were de novo assembled, consisting of 87 protein-coding genes, 36 tRNA genes, and 8 rRNA genes. A comparative analysis was conducted between the chloroplast genome of P. longitubus and three other published species of Petrocodon. The chloroplast genome of four Petrocodon species was found to have a double-chain ring structure, with a size ranging from 152,958 to 153,292 bp. Chloroplast genome size had indistinguishable. Four Petrocodon species was ra elatively conserved sequence, with 87 or 88 protein-coding genes, and 8 rRNA were the most conserved, which contains 42 ~ 50 SSR sites, which are mainly mononucleotides and dinucleotides, 4 boundary transition regions, then trinucleotides, pentanucleotides and hexanucleotides have been not detected. The non-preferred codons of the chloroplast genome in the four Petrocodon species are those ending in A, C, G, or T. The chloroplast genomes of these four Petrocodon species are highly similar to each other and to several Primulina species. Phylogenetic trees indicate that P. longitubus and other Petrocodon species were grouped together in a clade, with P. longitubus form a single clade. The results support the scientific naming of P. Longitubusr based on horticultural traits and further clarify the systematic status using molecular information.