Phylogeny and evolutionary history of <it>Leymus </it>(Triticeae; Poaceae) based on a single-copy nuclear gene encoding plastid acetyl-CoA carboxylase

• Main Authors: Ding Cun-Bang, Kang Hou-Yang, Zhang Hai-Qin, Yang Rui-Wu, Sha Li-Na, Fan Xing, Zhang Li, Zheng You-Liang, Zhou Yong-Hong
• Format: Article
• Language: English
• Published: BMC 2009-10-01
• Series: BMC Evolutionary Biology
• Online Access: http://www.biomedcentral.com/1471-2148/9/247

<p>Abstract</p> <p>Background</p> <p>Single- and low- copy genes are less likely subject to concerted evolution, thus making themselves ideal tools for studying the origin and evolution of polyploid taxa. <it>Leymus </it>is a polyploid genus with a diverse array of morphology, ecology and distribution in Triticeae. The genomic constitution of <it>Leymus </it>was assigned as NsXm, where Ns was presumed to be originated from <it>Psathyrostachys</it>, while Xm represented a genome of unknown origin. In addition, little is known about the evolutionary history of <it>Leymus</it>. Here, we investigate the phylogenetic relationship, genome donor, and evolutionary history of <it>Leymus </it>based on a single-copy nuclear <it>Acc1 </it>gene.</p> <p>Results</p> <p>Two homoeologues of the <it>Acc1 </it>gene were isolated from nearly all the sampled <it>Leymus </it>species using allele-specific primer and were analyzed with those from 35 diploid taxa representing 18 basic genomes in Triticeae. Sequence diversity patterns and genealogical analysis suggested that (1) <it>Leymus </it>is closely related to <it>Psathyrostachys</it>, <it>Agropyron</it>, and <it>Eremopyrum</it>; (2) <it>Psathyrostachys juncea </it>is an ancestral Ns-genome donor of <it>Leymus </it>species; (3) the Xm genome in <it>Leymus </it>may be originated from an ancestral lineage of <it>Agropyron </it>and <it>Eremopyrum triticeum</it>; (4) the <it>Acc1 </it>sequences of <it>Leymus </it>species from the Qinghai-Tibetan plateau are evolutionarily distinct; (5) North America <it>Leymus </it>species might originate from colonization via the Bering land bridge; (6) <it>Leymus </it>originated about 11-12MYA in Eurasia, and adaptive radiation might have occurred in <it>Leymus </it>during the period of 3.7-4.3 MYA and 1.7-2.1 MYA.</p> <p>Conclusion</p> <p><it>Leymus </it>species have allopolyploid origin. It is hypothesized that the adaptive radiation of <it>Leymus </it>species might have been triggered by the recent upliftings of the Qinghai-Tibetan plateau and subsequent climatic oscillations. Adaptive radiation may have promoted the rapid speciation, as well as the fixation of unique morphological characters in <it>Leymus</it>. Our results shed new light on our understanding of the origin of Xm genome, the polyploidization events and evolutionary history of <it>Leymus </it>that could account for the rich diversity and ecological adaptation of <it>Leymus </it>species.</p>