Origin and Reticulate Evolutionary Process of Wheatgrass Elymus trachycaulus (Triticeae: Poaceae).

Hongwei Zuo,Dexiang Wu,Panpan Wu,Genlou Sun,Wujun Ma

doi:10.1371/journal.pone.0125417

Hongwei Zuo, Dexiang Wu + Show 3 more

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https://doi.org/10.1371/journal.pone.0125417

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Journal: PloS one	Publication Date: May 6, 2015
Citations: 49	License type: CC BY 4.0

Affiliation: Anhui Agricultural University, Saint Mary's University

Abstract

To study origin and evolutionary dynamics of tetraploid Elymus trachycaulus that has been cytologically defined as containing StH genomes, thirteen accessions of E. trachycaulus were analyzed using two low-copy nuclear gene Pepc (phosphoenolpyruvate carboxylase) and Rpb2 (the second largest subunit of RNA polymerase II), and one chloroplast region trnL–trnF (spacer between the tRNA Leu (UAA) gene and the tRNA-Phe (GAA) gene). Our chloroplast data indicated that Pseudoroegneria (St genome) was the maternal donor of E. trachycaulus. Rpb2 data indicated that the St genome in E. trachycaulus was originated from either P. strigosa, P. stipifolia, P. spicata or P. geniculate. The Hordeum (H genome)-like sequences of E. trachycaulus are polyphyletic in the Pepc tree, suggesting that the H genome in E. trachycaulus was contributed by multiple sources, whether due to multiple origins or introgression resulting from subsequent hybridization. Failure to recovering St copy of Pepc sequence in most accessions of E. trachycaulus might be caused by genome convergent evolution in allopolyploids. Multiple copies of H-like Pepc sequence from each accession with relative large deletions and insertions might be caused by either instability of Pepc sequence in H- genome or incomplete concerted evolution. Our results highlighted complex evolutionary history of E. trachycaulus.

Highlights

Interspecific or intergeneric hybridization and polyploidization are two widespread and evolutionarily important phenomena in plants, which play important roles in the formation of new allopolyploid species [1,2,3]
Previous studies using cpDNA sequences have confirmed that the diploid St genome species, Pseudoroegneria, is the maternal donor of E. trachycaulus [41, 54,55,56]
Our result is consistent with a study based on combined cpDNA restriction sites, rpoA sequences, and tRNA spacer sequences, in which the several North American Elymus species including E. trachycaulus were grouped with Pseudoroegneria, Thinopyrum and Dasypyrum [41]

Summary

Introduction

Interspecific or intergeneric hybridization and polyploidization are two widespread and evolutionarily important phenomena in plants, which play important roles in the formation of new allopolyploid species [1,2,3]. Numerous studies have indicated that many intra- and inter-genomic changes that accompanied allopolyploid formation such as rapid elimination and recombination of low-copy sequence fragment, DNA methylation pattern changes, retrotransposon activation, intergenomic conversion and epigenetic changes, might have produced a more harmonious behavior and activity of the different constituent genomes. Those genomic alterations exhibited different evolutionary dynamics which might lead to genetic asymmetry evolution resulting in conformity and convergent effects [4,5,6,7,8,9].

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