Origin and Evolution of Allopolyploid Wheatgrass Elymus fibrosus (Schrenk) Tzvelev (Poaceae: Triticeae) Reveals the Effect of Its Origination on Genetic Diversity

Characterization of the complete chloroplast genome of Elymus alashanicus (Keng) S. L. Chen, and its phylogenetic analysis

Elymus alashanicus (Keng) S. L. Chen, a herbaceous plant endemic to China, plays a crucial role in the local ecosystems. In this study, we sequenced and characterized the complete chloroplast (cp) genome of E. alashanicus, which is 135,072 bp in length and arranged in a circular form. The cp genome includes a pair of inverted repeats (IRa and IRb) of 20,813 bp each, separated by a large single-copy (LSC) region of 80,678 bp and a small single-copy (SSC) region of 12,768 bp. The cp genome contains 130 genes, including 83 protein-coding genes, 39 tRNA genes, and eight rRNA genes. Phylogenetic analysis revealed that E. alashanicus is closely related to Elymus breviaristatus and Campeiostachys dahurica var. tangutorum in current sampling. Our findings provide valuable insights into the cp genome of E. alashanicus, which could contribute to further studies on the evolution and conservation of this species.

Genome constitution and evolution of Elytrigia lolioides inferred from Acc1, EF-G, ITS, TrnL-F sequences and GISH

BACKGROUND

Elytrigia lolioides (Kar. et Kir.) Nevski, which is a perennial, cross-pollinating wheatgrass that is distributed in Russia and Kazakhstan, is classified into Elytrigia, Elymus, and Lophopyrum genera by taxonomists on the basis of different taxonomic classification systems. However, the genomic constitution of E. lolioides is still unknown. To identify the genome constitution and evolution of E. lolioides, we used single-copy nuclear genes acetyl-CoA carboxylase (Acc1) and elongation factor G (EF-G), multi-copy nuclear gene internal transcribed space (ITS), chloroplast gene trnL-F together with fluorescence and genomic in situ hybridization.

RESULTS

Despite the widespread homogenization of ITS sequences, two distinct lineages (genera Pseudoroegneria and Hordeum) were identified. Acc1 and EF-G sequences suggested that in addition to Pseudoroegneria and Hordeum, unknown genome was the third potential donor of E. lolioides. Data from chloroplast DNA showed that Pseudoroegneria is the maternal donor of E. lolioides. Data from specific FISH marker for St genome indicated that E. lolioides has two sets of St genomes. Both genomic in situ hybridization (GISH) and fluorescence in situ hybridization (FISH) results confirmed the presence of Hordeum genome in this species. When E genome was used as the probe, no signal was found in 42 chromosomes. The E-like copy of Acc1 sequences was detected in E. lolioides possibly due to the introgression from E genome species. One of the H chromosomes in the accession W6-26586 from Kazakhstan did not hybridize H genome signals but had St genome signals on the pericentromeric regions in the two-color GISH.

CONCLUSIONS

Phylogenetic and in situ hybridization indicated the presence of two sets of Pseudoroegneria and one set of Hordeum genome in E. lolioides. The genome formula of E. lolioides was designed as StStStStHH. E. lolioides may have originated through the hybridization between tetraploid Elymus (StH) and diploid Pseudoroegneria species. E and unknown genomes may participate in the speciation of E. lolioides through introgression. According to the genome classification system, E. lolioides should be transferred into Elymus L. and renamed as Elymus lolioidus (Kar. er Kir.) Meld.