Nucleotide variation and secondary structures of nuclear ribosomal ITS۲ in phylogeny relationships of some wheat species

This research aimed to estimate the nucleotide polymorphism and point mutation/substitutions for ITS۲ region in ۱۲ different Triticum and Aegilops species, and to demonstrate their phylogenetic relationships. The aligned ITS۲ dataset showed a total of ۶۷ SNPs and transitions (۷۵%) predominant over transversions (۲۵%). The C/T transitions were observed at highest level in the studied species. The highest nucleotide substitutions occurred in ITS۲ sequences of T. aestivum, T. turgidum, and A. speltoides that showed similar substitutions on the base sites ۷۶, ۱۹۳, ۲۱۵, ۲۳۰ and ۲۴۱ (TCCAG changed to ATTTA). T. boeticum and T. urartu showed similar substitutions on the base sites ۸۵, ۲۰۱, ۲۳۱, ۲۳۴ and ۲۵۲ (GTGCC changed to AGATA). Remarkably, the nucleotide of base site ۱۴۶ was C in all Triticum species, but T in all Aegilops species. The substitution rate in A. neglecta, and A. umbellulata was zero, it was concluded that their ITS۲ is conserved. The secondary structures of ITS۲ in the studied species was similar to that of the other flowering plants with four helices and the variation in helices length. The helix III had the longest length compared to the other helices. The length ranges of helices I, II, IV varied from ۹ (T. turgidum, and T. urartu) to ۱۰, ۱۱ (A. cylindrica) ۱۳ and ۶ (A. speltoides) and ۱۰ (T. boeticum) paired bases, respectively. Using pairwise ITS۲ nucleotide comparisons, the closeness of A. caudata with A. cylindrica, T. boeticum with T. urartu, A. neglecta with A. umbellulata was observed. Phylogeny trees classified ۱۲ species into four main clades. The highest point mutations occurred in ITS۲ sequences related to the species grouped in the first clade.

کلیدواژه ها:

Aegilops ، ITS ، Point mutation ، Phylogeny ، Wheat