Complete plastid genome of Crotalaria sessiliflora (Fabaceae): Insights into plastome structure, rps16 pseudogenization, and phylogenetic implications

Plastid genomes (plastomes) provide valuable insights into evolutionary relationships in legumes, but many lineages remain under-sampled. The genus Crotalaria (∼700 species) is especially underrepresented, with only three complete plastomes published to date. Crotalaria sessiliflora is an ecologically important, nitrogen-fixing herb valued in traditional medicine, yet its plastome has not been previously reported. Here, we present the first complete plastome of C. sessiliflora and analyze its structure and evolution. Using next-generation sequencing, we assembled and annotated the 153,085 bp plastome and performed comparative analyses with three other Crotalaria species, including codon usage assessment, gene content comparison, and plastome-based phylogenetic reconstruction. The C. sessiliflora plastome displays a typical quadripartite structure and contains 127 genes (82 protein-coding). Its genomic architecture is typical of genistoid taxa that have experienced the canonical ∼50-kb inversion and a ∼36-kb inversion. Notably, the plastid rps16 gene is pseudogenized in C. sessiliflora , representing a lineage-specific gene loss that reduces its functional gene count relative to other species. Plastome phylogenomic analysis places C. sessiliflora in a well-supported clade with its congeners, confirming its phylogenetic position within Crotalaria . This first plastome resource for C. sessiliflora fills a critical gap and provides new insights into plastome evolution and systematics in the Fabaceae.