Spontaneous whole-genome duplication restores fertility in interspecific hybrids

Abstract

Interspecies hybrids often show some advantages over parents but also frequently suffer from reduced fertility, which can sometimes be overcome through sexual reproduction that sorts out genetic incompatibilities. Sex is however inefficient due to the low viability or fertility of hybrid offspring and thus limits their evolutionary potential. Mitotic cell division could be an alternative to fertility recovery in species such as fungi that can also propagate asexually. Here, to test this, we evolve in parallel and under relaxed selection more than 600 diploid yeast inter-specific hybrids that span from 100,000 to 15 M years of divergence. We find that hybrids can recover fertility spontaneously and rapidly through whole-genome duplication. These events occur in both hybrids between young and well-established species. Our results show that the instability of ploidy in hybrid is an accessible path to spontaneous fertility recovery.

The Genome Sequence of the Jean-Talon Strain, an Archeological Beer Yeast from Québec, Reveals Traces of Adaptation to Specific Brewing Conditions

“…Similar results from Gallone et al 2016 andGonçalves et al 2016 showed that multiple populations of beer strains had high rates of tetraploidy. Although spontaneous yeast tetraploids are usually fertile (Charron et al 2019), the Jean-Talon strain shows about 30% spore viability ( Figure 1C), which is close to the average spore viability observed for beers from the genetic groups Beer2, Mixed and Mosaic in (Gallone et al 2016). The Jean-Talon is therefore typical of beer strains with respect to ploidy and fertility.…”

“…Measurement of DNA content was performed using flow cytometry and the SYTOX green staining assay (Thermo Fisher, Waltham, USA) as done in (Charron et al 2019). Cells were first thawed from glycerol stock and streaked on solid YPD in six petri dishes (room temperature, three days) to obtain isolated colonies.…”

The effect of hybridization on transposable element accumulation in an undomesticated fungal species

“…Moreover, natural hybrids are somewhat limited in their ability to uncover the interplay between hybridization and transposition, as they are relatively recent introgressed lineages that resulted from admixture between closely related lineages. To systematically explore the effect of hybridization on Ty transposition rates, we performed a large-scale mutation accumulation (MA) experiment on 11 artificial hybrid backgrounds, eight of which were previously published (Charron et al, 2019). A MA experiment with yeast consists of subjecting a population to periodic single-cell bottlenecks (typically during hundreds to thousands of mitotic generations) by streaking a randomly chosen single colony, thus amplifying genetic drift and making natural selection inefficient (Lynch et al, 2008) (Figure 6a).…”

“…Crosses BB, BC, BA and BSc were previously published (Charron et al, 2019). CC crosses were performed following the same methodology.…”

“…Scatter plots (CCPR plots) show the partial residuals for each independent variable, along with the fitted regression.We selected a random subset of 23 to 40 MA lines per cross and performed whole-genome resequencing on stocks frozen at Tini and Tend, totaling 372 strains sequenced at each timepoint (PRJNA515073). All these strains were confirmed to be diploid at Tini and Tend by quantifying total DNA content using flow cytometry((Charron et al, 2019), Marsit et al in prep). Focusing on full-length Ty1, Ty3p and Tsu4, no global trend emerged from the variation of NRD before and after MA(Figure 6e,…”