Although a few plant lineages have lost one copy of the plastid genome (plastome) inverted repeat (IR), its near ubiquity among streptophytes has fostered speculation about its functional role and consequent evolutionary significance. To evaluate hypotheses of its persistence, Blazier et al. sequenced plastomes of Erodium (Geraniaceae), where several species have lost the IR structure and found that the plastomes of one derived clade surprisingly contained a large IR.
Comparative analyses across the genus suggest that the IR per se does not stabilize plastome structure but rather, like bacterial endosymbiont genomes, increased proportions of non-IR recombinogenic repeats likely contribute to genomic instability in Erodium.
John C. Blazier, Robert K. Jansen, Jeffrey P. Mower, Madhu Govindu, Jin Zhang, Mao-Lun Weng, Tracey A. Ruhlman, 2016, 'Variable presence of the inverted repeat and plastome stability in Erodium', Annals of Botany, vol. 117, no. 7, pp. 1209-1220 http://dx.doi.org/10.1093/aob/mcw065