期刊
GENOME BIOLOGY AND EVOLUTION
卷 13, 期 2, 页码 -出版社
OXFORD UNIV PRESS
DOI: 10.1093/gbe/evaa236
关键词
transcriptome; genome evolution; unbiased subgenome evolution; allotetraploid; Ephedra; gymnosperm
资金
- Key Research Programof Frontier Sciences, the Chinese Academy of Sciences [QYZDJ-SSW-SMC027]
- National Key Research and Development Program of China [2017YFA0605100]
- National Natural Science Foundation of China [31330008, 31170197]
By analyzing the transcriptomes of allopolyploid species of Ephedra and their putative diploid progenitors, this study found an unbiased subgenome evolution in Ephedra, with subgenome divergence at around 8 million years ago, implying that the formation of large genomes in gymnosperms may be attributed to even and slow fractionation following polyploidization.
The evolutionary dynamics of polyploid genomes and consequences of polyploidy have been studied extensively in angiosperms but very rarely in gymnosperms. The gymnospermous genus Ephedra is characterized by a high frequency of polyploidy, and thus provides an ideal system to investigate the evolutionary mode of allopolyploid genomes and test whether subgenome dominance has occurred in gymnosperms. Here, we sequenced transcriptomes of two allotetraploid species of Ephedra and their putative diploid progenitors, identified expressed homeologs, and analyzed alternative splicing and homeolog expression based on PacBio Iso-Seq and Illumina RNA-seq data. We found that the two subgenomes of the allotetraploids had similar numbers of expressed homeologs, similar percentages of homeologs with dominant expression, and approximately equal numbers of isoforms with alternative splicing, showing an unbiased subgenome evolution as in a few polyploid angiosperms, with a divergence of the two subgenomes at similar to 8 Ma. In addition, the nuclear DNA content of the allotetraploid species is almost equal to the sum of two putative progenitors, suggesting limited genome restructuring after allotetraploid speciation. The allopolyploid species of Ephedra might have undergone slow diploidization, and the unbiased subgenome evolution implies that the formation of large genomes in gymnosperms could be attributed to even and slow fractionation following polyploidization.
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