Parental transposable element loads influence their dynamics in young Nicotiana hybrids and allotetraploids.

This is the peer reviewed version of the following article: Mhiri, C., et al. (2018). "Parental transposable element loads influence their dynamics in young Nicotiana hybrids and allotetraploids." New Phytologist 0(0)., which has been published in final form at https://doi.org/10.1111/nph.15484. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived VersionsThe genomic shock hypothesis suggests that allopolyploidy is associated with genome changes driven by transposable elements, as a response to imbalances between parental insertion loads. To explore this hypothesis, we compared three allotetraploids, Nicotiana arentsii, N. rustica and N. tabacum, which arose over comparable time frames from hybridisation between increasingly divergent diploid species. We used sequence-specific amplification polymorphism (SSAP) to compare the dynamics of six transposable elements in these allopolyploids, their diploid progenitors and in corresponding synthetic hybrids. We show that element-specific dynamics in young Nicotiana allopolyploids reflect their dynamics in diploid progenitors. Transposable element mobilisation is not concomitant with immediate genome merger, but occurs within the first generations of allopolyploid formation. In natural allopolyploids, such mobilisations correlate with imbalances in the repeat profile of the parental species, which increases with their genetic divergence. Other restructuring leading to locus loss is immediate, nonrandom and targeted at specific subgenomes, independently of cross orientation. The correlation between transposable element mobilisation in allopolyploids and quantitative imbalances in parental transposable element loads supports the genome shock hypothesis proposed by McClintock.. The work was funded by the Association pour laRecherche sur les Nicotiane ́es (ARN; BTH01453 researchcontract), by the Agence Nationale de la Recherche (ANR-05-BDIV-015), by Campus France (PHC Barrande 09150SH,PHC Alliance 08782YM), by the Czech Science FoundationGA CR (501/12/G090 grant) and by Natural EnvironmentResearch Council. The IJPB benefits from the Agence Nationalede la Recherche through the Labex Saclay Plant Science-SPSproject (ANR-10-LABX-0040-SPS