The distribution and phylogenetic significance of a 50-kb chloroplast DNA inversion in the flowering plant family Leguminosae.

Species in 9 of the approximately 650 genera of the flowering plant family Leguminosae are known to possess a large (50-kb) inversion in their chloroplast genomes, relative to the gene order found most commonly among land plants. Putatively basal elements of the family have not been surveyed for the inversion, which is unknown outside the legumes. Using a combination of polymerase chain reaction and restriction-mapping approaches employing primers or hybridization probes flanking inversion endpoints, 132 legume genera were screened for the presence of the inversion. The inversion was found to be absent in all taxa from two of the three subfamilies (Mimosoideae and Caesalpinioideae), whereas the inversion was found to be present in most taxa of the third subfamily (Papilionoideae). Two papilionoid tribes, Swartzieae and Sophoreae, were heterogeneous for the inversion, which is consistent with a number of lines of evidence suggesting the polyphyly of these tribes. The 50-kb inversion appears to be a unique event in the evolution of Leguminosae, providing a synapomorphy for a clade that includes most of the Papilionoideae.