Abstract
BackgroundPolyploid species often originate recurrently. While this is well known, there is little information on the extent to which distinct allotetraploid species formed from the same parent species differ in gene expression. The tetraploid yarrow species Achillea alpina and A. wilsoniana arose independently from allopolyploidization between diploid A. acuminata and A. asiatica. The genetics and geography of these origins are clear from previous studies, providing a solid basis for comparing gene expression patterns of sibling allopolyploid species that arose independently.ResultsWe conducted comparative RNA-sequencing analyses on the two Achillea tetraploid species and their diploid progenitors to evaluate: 1) species-specific gene expression and coexpression across the four species; 2) patterns of inheritance of parental gene expression; 3) parental contributions to gene expression in the allotetraploid species, and homeolog expression bias. Diploid A. asiatica showed a higher contribution than diploid A. acuminata to the transcriptomes of both tetraploids and also greater homeolog bias in these transcriptomes, possibly reflecting a maternal effect. Comparing expressed genes in the two allotetraploids, we found expression of ca. 30% genes were species-specific in each, which were most enriched for GO terms pertaining to “defense response”. Despite species-specific and differentially expressed genes between the two allotetraploids, they display similar transcriptome changes in comparison to their diploid progenitors.ConclusionTwo independently originated Achillea allotetraploid species exhibited difference in gene expression, some of which must be related to differential adaptation during their post-speciation evolution. On the other hand, they showed similar expression profiles when compared to their progenitors. This similarity might be expected when pairs of merged diploid genomes in tetraploids are similar, as is the case in these two particular allotetraploids.
Highlights
IntroductionPolyploid species often consist of lineages that originated independently and recurrently from the same parental species [20, 21]
In the orchid genus, Dactylorhiza, has research been conducted on gene expression and epigenetic differences among sibling allotetraploids derived from the same parental species pair
To shed further light on how gene expression might differ between allopolyploid species that originated independently from the same progenitor species, we focus here on two allotetraploid yarrow species, Achillea alpina L. and A. wilsoniana Heimerl ex Hand. -Mazz., and their parental species, A. acuminata (Ledeb.) Sch. -Bip. and A. asiatica Serg. (Asteraceae)
Summary
Polyploid species often consist of lineages that originated independently and recurrently from the same parental species [20, 21] Such recurrent formation can result in karyotypic, genomic, transcriptomic and phenotypic variation across lineages as demonstrated in recently originated allotetraploid species of Tragopogon (Asteraceae) [22,23,24,25,26,27]. In the orchid genus, Dactylorhiza, has research been conducted on gene expression and epigenetic differences among sibling allotetraploids derived from the same parental species pair. This showed that both kinds of differences occurred and were stable among these allotetraploid species, raising the possibility that they reflect divergent adaptation to the different environmental conditions experienced by the species [28, 29]
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