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Abstract Detail

Hybrids and Hybridization

Wolfe, Thomas [1], Francisco, Balao Robles [2], Emiliano Trucchi, Trucchi [1], Maite, Lorenzo [2], Juliane, Baar [1], Ovidiu, Paun [1].

The transcriptomic drivers of ecological divergence after recurrent allopolyploidization in Dactylorhiza (Orchidaceae).

Recurrent, polytopic origins are widespread among polyploids. These can produce a multitude of genetically, ecologically, morphologically and physiologically distinct populations. Subsequent gene flow, independent assortment and recombination may produce additional variation that will be sorted by natural selection as a function of local conditions. Our understanding of the ecological relevance of such early processes in young polyploids is still in its infancy. As their multiple origins provide natural replicates, sibling allopolyploids are excellent models to uncover mechanisms of adaptation to divergent environments, which are assumed to lead to evolutionary diversification and biodiversity increase. We screened the transcriptomic diversity among ecologically divergent, European sibling allopolyploid orchids (D. majalis and D. traunsteineri) of different moderate ages (i.e., less than 15,000 years) in order to identify the mechanisms driving their phenotypic divergence. These allopolyploids were formed through unidirectional hybridization between diploids D. fuchsii (always the maternal parent) and D. incarnata. Using RNA-seq we specifically test the hypothesis that over short evolutionary times, like in our study system, their ecological divergence relies mainly on quantitative differential gene expression (DE) rather than differences in coding DNA sequence. We observe a general trend of increased overexpression of genes in the youngest polyploid in comparison to the older D. majalis, whose transcriptome resembles more a diploid state. The phenotypic divergence between the polyploids is mediated by a general parental dominance in opposite directions, a pattern partly retained also at the level of transgressively expressed transcripts. The DE between the polyploids affects several ecologically-relevant genes. For example, genes in the nitrate metabolic pathway have been significantly downregulated after allopolyploidization in D. traunsteineri, which appears adapted to nitrogen-poor environments. In addition, the nucleotidic nature of RNA-seq allows us to ask specific questions about patterns of recombination between polyploid sub-genomes and introgression with diploid parental genomes. With smRNA-seq we also investigate the divergence in post-transcriptional regulation and the activity of transposable elements. The differential regulation via smRNAs appears however less systemic than the observed transcriptional divergence, and affects a different population of transcripts, but, in part, similar processes and functions. Our results add to our growing comprehension of the broader consequences of polyploidy, a central force behind plant evolution.

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Related Links:

1 - University of Vienna, Rennweg 14, Vienna, 1030, Austria
2 - Facultad de Biologia, Avda. Reina Mercedes, 6, Sevilla, 41012 , Spain
3 - University of Vienna, Rennweg 14, Vienna, 1030, Austria

Differential gene expression
Homeolog expression bias
Expression level dominance.

Presentation Type: Oral Paper
Session: 22, Hybrids and Hybridization
Location: Sundance 1/Omni Hotel
Date: Tuesday, June 27th, 2017
Time: 9:15 AM
Number: 22004
Abstract ID:229
Candidate for Awards:Margaret Menzel Award

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