Abstract Detail

Hybrids and Hybridization

Eriksson , Mimmi Cecilia [1], Temsch, Eva [1], McCann, Jamie [2], Paun, Ovidiu [1].

Repetitive elements and early stages of polyploid evolution. A perspective from sibling allopolyploid marsh orchids (Dactylorhiza).

Whole-genome duplication (WGD) and hybridization are among the most powerful forces in the evolution of angiosperms and other groups. The formation of an allopolyploid may trigger a genomic shock and a plethora of cascading responses, including alteration of the epigenetic landscape and activation of transposable elements (TEs). In this context, TE activity is believed to be initially stochastic with regards to TE type, the activated allele and the insert positions, but its phenotypic effects (if any) are immediately subject to natural selection. To further understand the role and fate of TEs in early stages after allopolyploidization the orchid genus Dactylorhiza offers an intriguing study system. With a sequential array of postglacial, sibling allotetraploids formed by unidirectional hybridisation between the highly divergent diploids D. fuchsii and D. incarnata serving as natural biological replicates, we can address TE composition dynamics at different time-points after formation. The parental diploid lineages feature a different demographic history and genome size differences (1C values: D. fuchsii 2.9 pg, D. incarnata 3.6 pg), the larger genome of the paternal parent appears to be driven by a recent expansion of TEs, in particular LTR retrotransposons of the subclass Ty1/copia. We find that the genome size and TE composition for the five investigated allopolyploid lineages are largely additive with respect to the parents and exhibit relatively small differences among each other. However, due to their large genome size (2C ~ 13 Gb) the observed differences are on the same order of magnitude as the entire genomes of some plants such as Arabidopsis thaliana. We find one element type which diverges significantly from the additive expectation and is one of the main drivers of observed genome dynamics among the sibling allopolyploids. This highly dynamic element is found in higher proportions in the maternal parental species, which also has the smallest genome of the two parents. This element was determined to be a Miniature Inverted-repeat Transposable Element (MITE). Our result suggests that the fate of TEs in the allopolyploid species is strongly regulated and predictable, with no significant genomic shock following any of the allopolyploid speciation events (with regard to TEs).

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1 - University of Vienna, Department of Botany and Biodiversity Research, Rennweg 14, Vienna, 1030, Austria
2 - Biology Centre of the Czech Academy of Sciences, Institute of Plant Molecular Biology, Ceske Budejovice, 37005, Czech Republic

transposable elements
genomic shock

Presentation Type: Oral Paper
Session: HYHY1, Hybrids and Hybridization
Location: Virtual/Virtual
Date: Monday, July 27th, 2020
Time: 1:15 PM
Number: HYHY1004
Abstract ID:589
Candidate for Awards:None

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