Dominance in gene expression variability during ontogeny reveals the importance of canalization in adaptive divergence and speciation.
Ontology highlight
ABSTRACT:
ORGANISM(S): Salvelinus alpinus
PROVIDER: GSE193797 | GEO | 2023/01/01
REPOSITORIES: GEO
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Project description:Background: The Dobzhansky-Muller (D-M) model of speciation by genic incompatibility is widely accepted as the primary cause of interspecific postzygotic isolation. Since the introduction of this model, there have been theoretical and experimental data supporting the existence of such incompatibilities. However, speciation genes have been largely elusive, with only a handful of candidate genes identified in a few organisms. The Saccharomyces sensu stricto yeasts have small genomes, can be easily cultured, and can mate interspecifically to produce sterile hybrids, are thus an ideal model for studying postzygotic isolation. Among them, only a single D-M pair has been found, between S. bayanus and S. cerevisiae, comprising the mitochondrially targeted product of a nuclear gene, AEP2, and a mitochondrially encoded locus, OLI1, the 5' region of whose transcript is bound by Aep2. Thus far, no D-M pair of nuclear genes has been identified between any sensu stricto yeasts. Methods: We report here the first detailed genome-wide analysis of rare F2 progeny from an otherwise sterile hybrid, and show that no classic D-M pairs of speciation genes exist between the nuclear genomes of the closely related yeasts S. cerevisiae and S. paradoxus. Instead, our analyses suggest that more complex interactions may be responsible for their post-zygotic separation. These interactions most likely involve multiple loci having weak effects, as there were multiple significant pairwise combinations of loci, with no single combination being completely excluded from the viable F2s. Conclusions: The lack of a nuclear encoded classic D-M pair between these two yeasts, yet the existence of multiple loci that may each exert a small effect through complex interactions, suggests that initial speciation events might not always be mediated by D-M pairs. An alternative explanation may be that "death by a thousand cuts" leads to speciation, whereby an accumulation of polymorphisms can lead to an incompatibility between the species "transcriptional and metabolic networks, with no single pair at least initially being responsible for the incompatibility. After such a speciation event, it is possible that one or more D-M pairs might subsequently arise following isolation. Genotypes for hybrids between S. cerevisiae and S. paradoxus. A genotyping experiment design type classifies an individual or group of individuals on the basis of alleles, haplotypes, SNP's.
2010-06-08 | GSE19683 | GEO
Project description:Parental effects represent an important source of variation in offspring phenotypes. Depending on the specific mechanisms involved, parental effects may be caused to different degrees by either the maternal or paternal parent, and these effects may in turn act at different stages of development. In order to detect parental effects acting on gene transcription regulation and length phenotype during ontogeny, the transcriptomic profiles of two reciprocal hybrids from Laval × Rupert and Laval × domestic populations of brook charr were compared at hatching, yolk sac resorption, and 15 weeks after exogenous feeding. Using a salmonid cDNA microarray, our results show that parental effects modulated gene expression among reciprocal hybrids only at the yolk sac resorption stage. In addition, Laval × domestic and Laval × Rupert reciprocal hybrids differed in the magnitude of theses parental effects, with 199 and 630 differentially expressed transcripts, respectively. This corresponds to a maximum of 18.5% of the analyzed transcripts. These transcripts are functionally related to cell cycle, nucleic acid metabolism and intracellular protein traffic, which is consistent with observed differences associated with embryonic development and growth differences in other fish species. Our results thus illustrate how parental effects on patterns of gene transcription seem dependent on the genetic architecture of the parents. In addition, in absence of transcriptomic differences, the non-transcriptomic deposits could also act to highlight the offspring differences in length before the yolk sac resorption.
2012-12-31 | GSE42435 | GEO
Project description:Parental effects represent an important source of variation in offspring phenotypes. Depending on the specific mechanisms involved, parental effects may be caused to different degrees by either the maternal or paternal parent, and these effects may in turn act at different stages of development. In order to detect parental effects acting on gene transcription regulation and length phenotype during ontogeny, the transcriptomic profiles of two reciprocal hybrids from LavalM-BM- M-CM-^WM-BM- Rupert and LavalM-BM- M-CM-^WM-BM- domestic populations of brook charr were compared at hatching, yolk sac resorption, and 15 weeks after exogenous feeding. Using a salmonid cDNA microarray, our results show that parental effects modulated gene expression among reciprocal hybrids only at the yolk sac resorption stage. In addition, LavalM-BM- M-CM-^WM-BM- domestic and LavalM-BM- M-CM-^WM-BM- Rupert reciprocal hybrids differed in the magnitude of theses parental effects, with 199 and 630 differentially expressed transcripts, respectively. This corresponds to a maximum of 18.5% of the analyzed transcripts. These transcripts are functionally related to cell cycle, nucleic acid metabolism and intracellular protein traffic, which is consistent with observed differences associated with embryonic development and growth differences in other fish species. Our results thus illustrate how parental effects on patterns of gene transcription seem dependent on the genetic architecture of the parents. In addition, in absence of transcriptomic differences, the non-transcriptomic deposits could also act to highlight the offspring differences in length before the yolk sac resorption. Pair-wise direct comparisons between 8 reciprocal hybrids (LavalRupert vs RupertLaval and LavalDomestic vs DomesticLaval) were performed at each developmental stage. For each developmental stage, cDNA of 8 samples from each cross were hybridized for a total of 48 microarrays analyzed. The distribution of dyes is equilibrated among each cross (4 samples with cy3 and 4 samples with Al647).
2012-12-31 | E-GEOD-42435 | biostudies-arrayexpress
Project description:Dominance in gene expression variability during ontogeny reveals the importance of canalization in adaptive divergence and speciation.
| PRJNA798013 | ENA
Project description:BackgroundSexual reproduction has classically been considered as a barrier to the buildup of discrete phenotypic differentiation. This notion has been confirmed by models of sympatric speciation in which a fixed genetic architecture and a linear genotype phenotype mapping were assumed. In this paper we study the influence of a flexible genetic architecture and non-linear genotype phenotype map on differentiation under sexual reproduction.We use an individual based model in which organisms have a genome containing genes and transcription factor binding sites. Mutations involve single genes or binding sites or stretches of genome. The genome codes for a regulatory network that determines the gene expression pattern and hence the phenotype of the organism, resulting in a non-linear genotype phenotype map. The organisms compete in a multi-niche environment, imposing selection for phenotypic differentiation.ResultsWe find as a generic outcome the evolution of discrete clusters of organisms adapted to different niches, despite random mating. Organisms from different clusters are distinct on the genotypic, the network and the phenotypic level. However, the genome and network differences are constrained to a subset of the genome locations, a process we call genotypic canalization. We demonstrate how this canalization leads to an increased robustness to recombination and increasing hybrid fitness. Finally, in case of assortative mating, we explain how this canalization increases the effectiveness of assortativeness.ConclusionWe conclude that in case of a flexible genetic architecture and a non-linear genotype phenotype mapping, sexual reproduction does not constrain phenotypic differentiation, but instead constrains the genotypic differences underlying it. We hypothesize that, as genotypic canalization enables differentiation despite random mating and increases the effectiveness of assortative mating, sympatric speciation is more likely than is commonly suggested.
| S-EPMC3224660 | biostudies-literature
Project description:Developmental mechanisms play an important role in determining the costs, limits, and evolutionary consequences of phenotypic plasticity. One issue central to these claims is the metaphor of developmental “decoupling,” where alternate morphs result from evolutionarily independent developmental pathways. We test this assumption through a microarray study that explores differences in gene expression between alternate morphs relative to differences between sexes, a classic example of developmental decoupling. We then examine whether morph-biased genes are less conserved, relative to morph-shared genes, as predicted if developmental decoupling relaxes pleiotropic constraints on divergence. We focus on the developing horns and brains of two species of horned beetles with spectacular sexual- and morph-dimorphism in the expression of horns and fighting behavior. We find that patterns of gene expression were as divergent between morphs as they were between sexes. However, overall patterns of gene expression were also highly correlated across morphs and sexes. Morph-biased genes were more evolutionarily divergent, suggesting a role of relaxed pleiotropic constraints or relaxed selection. Together these results suggest that alternate morphs are somewhat developmentally decoupled, and that this decoupling has significant evolutionary consequences. However, alternative morphs may not be as developmentally decoupled as sometimes assumed and such hypotheses of development should be revisited and refined.
2010-09-15 | GSE23425 | GEO
Project description:The genetic mechanisms underlying hybridization are poorly understood despite their potentially important roles in speciation processes, adaptative evolution, and agronomical innovation. In this study, transcription profiles were compared among three populations of brook charr and their hybrids using microarrays to assess the influence of hybrid origin on modes of transcription regulation inheritance and on the mechanisms underlying growth. We found that twice as many transcripts were differently expressed between the domestic strain and the two wild populations (Rupert and Laval) than between wild ones, despite their deeper genetic distance. This could reflect the consequence of artificial selection during domestication. We detected that hybrids exhibited strikingly different patterns of mode of transcription regulation, being mostly additive (94%) for domestic × Rupert, and non-additive for Laval × domestic (45.7%) and Rupert × Laval hybrids (37.5%). Both heterosis and outbreeding depression for growth were observed among the crosses. Our results indicated that prevalence of dominance in transcription regulation seems related to growth heterosis, while prevalence of transgressive transcription regulation may be more related to outbreeding depression. Our study clearly shows, for the first time in vertebrates, that the consequences of hybridization on both the transcriptome level and the phenotype are highly dependent on the specific genetic architectures of crossed populations and therefore hardly predictable. Comparison between six crosses using a loop design: direct comparison of hybrids vs parental populations fishes for 8 families. Each individual was technically replicated on two bi-coloured distinct microarrays and dye-swapped.
2010-07-01 | E-GEOD-22008 | biostudies-arrayexpress
Project description:Reproducibility in molecular and cellular studies is fundamental to scientific discovery. To establish the reproducibility of a well-defined long term neuronal differentiation protocol, we repeated the cellular and molecular comparison of the same two iPSC lines across five distinct laboratories. Despite uncovering acceptable variability within individual laboratories, we detect poor cross-site reproducibility of the differential gene expression signature between these two lines. Factor analysis identifies the laboratory as the largest source of variation along with several variation-inflating confounds such as passaging effects and progenitor storage. Single cell transcriptomics shows substantial cellular heterogeneity underlying inter-laboratory variability and being responsible for biases in differential gene expression inference. Factor analysis-based normalization of the combined dataset can remove the nuisance technical effects, enabling the execution of robust hypothesis generating studies. Our study shows that multi-center collaborations can expose systematic biases and identify critical factors to be standardized when publishing novel protocols, contributing to increased cross-site reproducibility.
2018-08-20 | GSE118734 | GEO