Fig. 1.—

A schematic explanation for the amplification of ancestral plastomic DNAs transferred from plastids to the nucleus. Top left: An ancestral plastomic fragment that includes F1 and F2 subfragments with a head-to-tail arrangement was transferred to the nucleus (top right) in the past. After this transfer, an inversion of F2 occurred, which resulted in a head-to-head arrangement of F1 and F2 in the extant plastome. Primers based on distinctive arrangements between ancestral and extant plastomes can facilitate specific amplification of transferred ancestral plastomic fragments and avoid contaminants from amplification of the extant plastome.