Complete Chloroplast Genome of and Dynamic Evolution in (Hypericaceae).

(St. John's Wort) is a medicinal plant from the Hypericaceae family. Here, we sequenced the whole chloroplast genome of and compared the genome variation among five species to discover dynamic changes and elucidate the mechanisms that lead to genome rearrangements in the chloroplast genomes. The chloroplast genome is 139,725 bp, exhibiting a circular quadripartite structure with two copies of inverted repeats (IRs) separating a large single-copy region and a small single-copy region. The chloroplast genome encodes 106 unique genes, including 73 protein-coding genes, 29 tRNAs, and 4 rRNAs. chloroplast genomes exhibit genome rearrangement and significant variations among species. The genome size variation among the five species was remarkably associated with the expansion or contraction of IR regions and gene losses. Three genes--UUU, , and -were lost, and three genes-, , and -were pseudogenized in . All the chloroplast genomes lost the two introns in , the intron in , and the second intron in . chloroplast genomes contain many long repeat sequences, suggesting a role in facilitating rearrangements. Most genes, according to molecular evolution assessments, are under purifying selection.