The chloroplast genome of Trollius acaulis: insights into comparative genomics and phylogenetic relationships

In this study, we de novo assembled the chloroplast (cp) genome of Trollius acaulis Lindl. (Ranunculaceae) and compared it with those of 16 other reported Trollius species. The cp genome of T. acaulis measured 159,961 base pairs (bps), consisting of a large single-copy region of 88,339 bp, a small single-copy region of 18,466 bp, and two inverted repeat regions of 26,578 bp each. Across the genus, cp genome lengths ranged from 159,597 to 160,611 bp, with large single-copy regions spanning 88,091–88,943 bp, small single-copy regions 18,083–18,532 bp, and IR regions 26,490–26,632 bp each. All Trollius cp genomes displayed a similar arrangement of 113 unique genes, including 79 protein-coding genes, 30 transfer RNA genes, and 4 ribosomal RNA genes. These genomes also exhibited similarities in terms of inverted repeats contraction/expansion, amino acid frequency, and codon usage patterns. Phylogenetic analysis divided the genus into three clades: T. acaulis formed a sister group with Trollius lilacinus Bunge in clade I (section Hegemone ), while the remaining 15 species were grouped into clades II and III (section Trollius ). This study advances our understanding of cp genome evolution in Trollius and clarifies its phylogenetic relationships.