Evolutionary pattern of rDNA following polyploidy in Leymus (Triticeae: Poaceae).
Ribosomal ITS polymorphism and its ancestral genome origin of polyploid Leymus were examined to infer the evolutionary outcome of rDNA gene following allopolyploid speciation and to elucidate the geographic pattern of ITS variation. The results demonstrated that different polyploids have experienced varying fates, including maintenance or homogenization of divergent arrays, occurrence of chimeric repeats and potential pseudogenes. Our data suggested that (1) the Ns, P/F, and St genomic types in Leymus were originated from Psathyrostachys, Agropyron/Eremopyrum, and Pseudoroegneria, respectively; (2) the occurrence of a higher proportion of Leymus species with predominant uniparental rDNA type might associate with the segmental allopolyploid origin, nucleolar dominance of alloploids, and rapid radiation of Leymus; (3) maintenance of multiple parental ITS types in allopolyploid might result from long generation times associated to vegetative multiplication, number and chromosomal location of ribosomal loci and/or recurrent hybridization; (4) the rDNA genealogical structure of Leymus species might associate with the geographic origins; and (5) ITS sequence clade shared by Leymus species from Central Asia, North America, and Nordic might be an outcome of ancestral ITS homogenization. Our results shed new light on understanding evolutionary outcomes of rDNA following allopolyploid speciation and geographic isolation.
Triticeae Research Institute, Sichuan Agricultural University, Wenjiang 611130, Sichuan, China; Key Laboratory of Crop Genetic Resources and Improvement, Ministry of Education, Sichuan Agricultural University, Yaan 625014, Sichuan, China.
Xing
X
Fan
Triticeae Research Institute, Sichuan Agricultural University, Wenjiang 611130, Sichuan, China.
Jing
J
Liu
Triticeae Research Institute, Sichuan Agricultural University, Wenjiang 611130, Sichuan, China.
Li-Na
LN
Sha
Biology Department, Saint Mary's University, Halifax NS B3H 3C3, Canada.
Gen-Lou
GL
Sun
Triticeae Research Institute, Sichuan Agricultural University, Wenjiang 611130, Sichuan, China.
Zhi-Qin
ZQ
Hu
College of Resources and Environment, Sichuan Agricultural University, Wenjiang 611130, Sichuan, China.
Jian
J
Zeng
Triticeae Research Institute, Sichuan Agricultural University, Wenjiang 611130, Sichuan, China.
Hou-Yang
HY
Kang
Triticeae Research Institute, Sichuan Agricultural University, Wenjiang 611130, Sichuan, China.
Hai-Qin
HQ
Zhang
Triticeae Research Institute, Sichuan Agricultural University, Wenjiang 611130, Sichuan, China.
Yi
Y
Wang
College of Life Sciences, Sichuan Agricultural University, Yaan 625014, Sichuan, China.
Xiao-Li
XL
Wang
College of Life Sciences, Sichuan Agricultural University, Yaan 625014, Sichuan, China.
Li
L
Zhang
College of Life Sciences, Sichuan Agricultural University, Yaan 625014, Sichuan, China.
Chun-Bang
CB
Ding
College of Life Sciences, Sichuan Agricultural University, Yaan 625014, Sichuan, China.
Rui-Wu
RW
Yang
Triticeae Research Institute, Sichuan Agricultural University, Wenjiang 611130, Sichuan, China; Key Laboratory of Crop Genetic Resources and Improvement, Ministry of Education, Sichuan Agricultural University, Yaan 625014, Sichuan, China.
You-Liang
YL
Zheng
Triticeae Research Institute, Sichuan Agricultural University, Wenjiang 611130, Sichuan, China; Key Laboratory of Crop Genetic Resources and Improvement, Ministry of Education, Sichuan Agricultural University, Yaan 625014, Sichuan, China. Electronic address: zhouyh@sicau.edu.cn.
Yong-Hong
YH
Zhou
D004275:DNA, Ribosomal / Q000235:genetics*; D018745:Genome, Plant; D010802:Phylogeny; D006109:Poaceae / Q000145:classification / Q000235:genetics*; D011123:Polyploidy; D017422:Sequence Analysis, DNA
D004275:DNA, Ribosomal
Evolutionary pattern; Geographic origin; Leymus; Polyploidy; rDNA