Rapid evolution of promoters for the plastome gene ndhF in flowering plants

Plastome is thought to be a very conservative part of plant genome but little is known about the evolution of plastome promoters. It was previously shown that one light-regulated promoter (LRPpsbD) is highly conserved in different flowering plant species and in black pine. We have undertaken search and demonstrated that gene ndhF is located in a plastome region that rarely underwent substantial rearrangements in terrestrial plants. However, alignment of sequences upstream ndhF suggests that promoters of this gene underwent comparatively rapid evolution in flowering plants. Probably, the ancestor of two basal Magnoliophyta branches (magnoliids and eudicotyledons) had the promoter PA-ndhF, which was substituted with other promoters—PB-ndhF and PC-ndhF—in some phylogenetic lineages of dicots. We failed to reveal conservative sequences with potential promoters of −10/−35 type upstream ndhF genes of monocotyledonous plants, including nine representatives of the grass family (Poaceae). Multiple alignments of sequences from related taxa showed that the predicted ndhF promoters (A–C) underwent frequent mutations and these mutations are not only nucleotide substitutions but also small insertions and deletions. Thus, we can assume that at least some plastome promoters evolve rapidly.