Expression pattern of resynthesized allotetraploid Capsella is determined by hybridization, not whole-genome duplication

Polyploidization, the process leading to the increase in chromosome sets, is a major evolutionary transition in plants. Whole-genome duplication (WGD) within the same species gives rise to autopolyploids, whereas allopolyploids result from a compound process with two distinct components: WGD and interspecific hybridization. To dissect the instant effects of WGD and hybridization on gene expression and phenotype, we created a series of synthetic hybrid and polyploid Capsella plants, including diploid hybrids, autotetraploids of both parental species, and two kinds of resynthesized allotetraploids with different orders of WGD and hybridization. Hybridization played a major role in shaping the relative expression pattern of the neo-allopolyploids, whereas WGD had almost no immediate effect on relative gene expression pattern but, nonetheless, still affected phenotypes. No transposable element-mediated genomic shock scenario was observed in either neo-hybrids or neo-polyploids. Finally, WGD and hybridization interacted and the distorting effects of WGD were less strong in hybrids. Whole-genome duplication may even improve hybrid fertility. In summary, while the initial relative gene expression pattern in neo-allotetraploids was almost entirely determined by hybridization, WGD only had trivial effects on relative expression patterns, both processes interacted and had a strong impact on physical attributes and meiotic behaviors

How broad is the selfing syndrome? Insights from convergent evolution of gene expression across species and tissues in the Capsella genus

The shift from outcrossing to selfing is one of the main evolutionary transitions in plants. It is accompanied by profound effects on reproductive traits, the so-called selfing syndrome. Because the transition to selfing also implies deep genomic and ecological changes, one also expects to observe a genomic selfing syndrome. We took advantage of the three independent transitions from outcrossing to selfing in the Capsella genus to characterize the overall impact of mating system change on RNA expression, in flowers but also in leaves and roots. We quantified the extent of both selfing and genomic syndromes, and tested whether changes in expression corresponded to adaptation to selfing or to relaxed selection on traits that were constrained in outcrossers. Mating system change affected gene expression in all three tissues but more so in flowers than in roots and leaves. Gene expression in selfing species tended to converge in flowers but diverged in the two other tissues. Hence, convergent adaptation to selfing dominates in flowers, whereas genetic drift plays a more important role in leaves and roots. The effect of mating system transition is not limited to reproductive tissues and corresponds to both adaptation to selfing and relaxed selection on previously constrained traits

Pseudo-overdominance: how linkage and selection can interact and oppose to purging of deleterious mutations

International audienceA recommendation – based on reviews by Lei Zhao, Yaniv Brandvain and one anonymous reviewer – of the article: Awad DA, Waller D (2022) Conditions for maintaining and eroding pseudo-overdominance and its contribution to inbreeding depression. bioRxiv, 2021.12.16.473022, ver. 3 peer-reviewed and recommended by Peer Community in Evolutionary Biology. https://doi.org/10.1101/2021.12.16.47302

Dépression de consanguinité, systèmes de reproduction et biologie de la conservation. Approches théoriques et expérimentales chez Brassica insularis Moris

MONTPELLIER-BU Sciences (341722106) / SudocSudocFranceF

Mating system, Haldane’s sieve, and the domestication process

AGAP : équipe Génomique évolutive et gestion des populations (GE²pop)Mating systems are expected to have a strong influence on both the dynamic of adaptation and the genetic architecture of adaptive traits. In particular, the bias toward the fixation of dominant or partially dominant beneficialmutations predicted under outcrossing (Haldane’s sieve) is expected to be reduced under self-fertilization. To test this prediction in plants, we considered domestication as an example of adaptation. We compiled data from studies reporting the degree of dominance of quantitative trait loci (QTL) involved in the domestication syndrome. We found that adaptation to cultivation mostly proceeded through the selection of recessive and partially recessive genes in predominantly selfing species whereas a much larger fraction of domestication-related QTL were dominant or partially dominant in outcrossers, as expected under Haldane’s sieve. Our study also showed that levels of dominance in mixed mating crop species resemble those observed in selfers, suggesting that recessive alleles can contribute to adaptation even under moderate selfing rates. Although these results rely on a particular example of adaptation, they constitute one of the first attempts to test theoretical expectations on the level of dominance of genes involved in plant adaptation

Influence de la domestication et du système de reproduction sur la diversité et l'évolution des gènes chez les Triticeae

MONTPELLIER-BU Sciences (341722106) / SudocSudocFranceF