Evolution of plastid gene ycf4 in the inverted repeat lacking clade of legumes

The genome organization and gene content of plastome (plastid genome) are highly conserved among most flowering plant species. Plastome variation (in size and gene order) is rare in photosynthetic species but size variation, rearrangements, and gene/intron losses are attributed to groups of seed plants. Among the groups that display an appropriate level of variation for structural features, Fabaceae (legume family), in particular within the subfamily Papilionoideae and inverted repeat lacking clade (IRLC), presents the most dramatic structural change which provides an excellent model for the understanding of mechanisms of genomic evolution. IRLC comprises 52 genera (e.g., Wisteria, Glycyrrhiza, Astragalus, and Lathyrus) and ca 4000 species divided into seven tribes. In the present study, we have sampled several representatives from each tribe across IRLC from various herbaria and field, and encompassing all the major geographic areas of occurrence of the genera throughout the world, with emphasis on Iran. The ycf4 gene is located in the large single copy region of the plastid genome which is encoded a thylakoid protein that has been shown to play a role in regulating and assembly of photosystem I. ycf4 is more variable in the tribe Fabeae than in other tribes. In certain species of Lathyrus, Pisum and Vavilovia all belonging to Fabeae, the gene is either absent or a pseudogene. Our results showed that ycf4 is situated in a local mutation hotspot, in particular within tribe Fabeae, resulting in dramatic acceleration of sequence evolution in some species and evolutionary gene losses in others. Moreover, the genomic region around ycf4 including psaI gene at the upstream of it, in some species of Lathyrus has been lost.

کلیدواژه ها:

Plastome ، Fabaceae ، IRLC ، ycf4