Advances in the evolution of plastid genome structure in lycophytes and ferns

Abstract

Lycophyte and fern genetic research has accumulated over recent years due to sequencing technology advancement, making nuclear, plastid, and mitochondrial genomes accessible. While early plastid genome research focused on reporting genome structures and sequence characteristics, our current understanding spans comprehensively over structural evolution and phylogenomic analyses. These studies provide us with important insight for understanding the early evolution of vascular plants. Although lycophyte and fern plastid genomes are relatively well understood, this paper summarizes the current understanding of lycophyte and fern plastid genome structure and its variation. Such variation includes large inversions, boundary shifts of repeat regions, gene and intron loss, and some of which could be recognized as synapomorphies of higher taxonomic ranks. We also review RNA editing and long noncoding sequence inserts in plastid genomes, which are prevalent in lycophytes and ferns. However, the origin, mechanism and function of such remain unclear. We also comment on the application, merit and future of plastid phylogenomics.