Sequencing of the complete plastome of the thermal adder's-tongue fern, Kom. (Ophioglossaceae).

The Ophioglossaceae family, one of the oldest orders of extant ferns, exhibits diverse morphological and chromosomal characteristics. This study presents the first complete plastome sequence of thermal adder's-tongue fern (), a species renowned for its antioxidant properties in traditional Chinese medicine. Our analyses revealed 27 simple sequence repeats (SSRs) in the plastome, with variations in SSR frequencies compared to related genera. Our phylogenetic analyses placed within the s.s. clade, supporting previous studies and suggesting polyphyly within the genus based on the sensu PPG I system. The enlarged noncoding regions in fern organelles (ENRFOs) resulting from foreign DNA insertions in were identified in the and regions, similar to other species. ENRFOs were found at the LSC and SSC, but not in IRs in Ophioglossaceae. Consequently, foreign DNA insertions and lineage-specific SSRs shed light on plastome evolution in the Ophioglossaceae family.