Project description:Understanding the conditions that promote the evolution of reproductive isolation, and thus speciation. Here we empirically test some of the key predictions of speciation theory (Coyne 2004; Kohn 2005) by experimentally evolving the initial stages of speciation in yeast. After allowing replicate populations to adapt to two divergent environments, we observed the consistent, de novo evolution of two forms of postzygotic isolation: reduced rate of mitotic reproduction and reduced efficiency of meiotic reproduction. In general, divergent selection resulted in greater reproductive isolation than parallel selection, as predicted by ecological speciation theory. Our experimental system allowed for the first controlled comparison of the relative importance of ecological and genetic mechanisms of isolation, and the novel ability to quantify the effects of antagonistic epistasis. For mitotic reproduction, hybrid inferiority was conditional upon the selective environments and was both ecological and genetic in basis. In contrast, isolation associated with meiotic reproduction was unconditional and was caused solely by genetic mechanisms. Overall, our results show that adaption to divergent environments promotes the evolution of isolation through antagonistic epistasis, providing evidence of a plausible common avenue to speciation and adaptive radiation in nature (Schluter 2000,2001: Funk 2006) Keywords: Speciation, antagonistic epistasis, divergent adaptation
Project description:Ecological speciation is a common mechanism by which new species arise. Despite great efforts, the role of gene expression in ecological divergence and speciation is poorly understood. Here, we conducted a genome-wide gene expression investigation of two Oryza species that are evolutionarily young and distinct in ecology and morphology. Using digital gene expression (DGE) technology and the paired-end RNA sequencing (RNA-Seq) method, we obtained 21,415 expressed genes across three reproduction-related tissues at two critical developmental stages. Of them, ~8% (1717) differed significantly in expression levels between the two species and these differentially expressed genes are randomly distributed across the genome. Moreover, 62% (1064) of the differentially expressed genes exhibited a signature of directional selection in at least one species. Importantly, the genes with differential expression between species evolved more rapidly at the 5’flanking sequences than the genes without differential expression relative to coding sequences, suggesting that cis-regulatory changes are likely adaptive and play an important role in the ecological divergence of the two species. Finally, we showed evidence of significant differentiation between species in phenotype traits and observed that genes with differential expression were overrepresented with functional terms involving phenotypic and ecological differentiation between the two species, including reproduction- and stress-related characteristics. Our findings demonstrate that ecological speciation is associated with widespread and adaptive alterations in genome-wide gene expression and highlight the dominant role of regulatory evolution in ecological divergence and adaptation.
Project description:Ecological speciation is a common mechanism by which new species arise. Despite great efforts, the role of gene expression in ecological divergence and speciation is poorly understood. Here, we conducted a genome-wide gene expression investigation of two Oryza species that are evolutionarily young and distinct in ecology and morphology. Using digital gene expression (DGE) technology and the paired-end RNA sequencing (RNA-Seq) method, we obtained 21,415 expressed genes across three reproduction-related tissues at two critical developmental stages. Of them, ~8% (1717) differed significantly in expression levels between the two species and these differentially expressed genes are randomly distributed across the genome. Moreover, 62% (1064) of the differentially expressed genes exhibited a signature of directional selection in at least one species. Importantly, the genes with differential expression between species evolved more rapidly at the 5â??flanking sequences than the genes without differential expression relative to coding sequences, suggesting that cis-regulatory changes are likely adaptive and play an important role in the ecological divergence of the two species. Finally, we showed evidence of significant differentiation between species in phenotype traits and observed that genes with differential expression were overrepresented with functional terms involving phenotypic and ecological differentiation between the two species, including reproduction- and stress-related characteristics. Our findings demonstrate that ecological speciation is associated with widespread and adaptive alterations in genome-wide gene expression and highlight the dominant role of regulatory evolution in ecological divergence and adaptation. We selected accessions representing typical Oryza rufipogon and O. nivara, which were sampled exclusively from South and Southeast Asia where the two species overlap. We chose to collect three types of tissues, i.e., flag leaves at the heading stage (2â??7 cm above the primary branch) (L), panicles at the heading stage (H) and panicles at the flowering stage (10â??15 cm above the primary branch) (F). Sample collection was repeated twice in two consecutive years (2009 and 2010) under the same controlled conditions. A total of 36 samples were sequenced by Illuminaâ??s digital gene expression (DGE) system, with each type of tissues collected from six individuals of each species as biological replicates. To access the quality of DGE technology, we also selected six samples representing three tissues from each of two individuals (one individual per species) for paired-end RNA-Seq sequencing.
Project description:Induced pluripotent stem cells generated from patients with geographic atrophy as well as healthy individuals were differentiated to retinal pigment epithelium (RPE) cells. By integrating transcriptional profiles of 127,659 RPE cells generated from 43 individuals with geographic atrophy and 36 controls with genotype data, we identified 439 expression Quantitative Trait (eQTL) loci in cis that were associated with disease status and specific to subpopulations of RPE cells. We identified loci linked to two genes with known associations with geographic atrophy - PILRB and PRPH2, in addition to 43 genes with significant genotype x disease interactions that are candidates for novel genetic associations for geographic atrophy. On a transcriptome-only level, we identified molecular pathways significantly upregulated in geographic atrophy-RPE including in mitochondrial functions, metabolic pathways, and extracellular cellular matrix reorganisation. We subsequently implemented a large-scale proteomics analysis, confirming modification in proteins associated with these pathways. We also identified six significant protein (p) QTL that regulate protein expression in the RPE cells and in geographic atrophy - two of which share variants with cis-eQTL, including proteins involve in mitochondrial biology and neuodegeneration. Investigation of mitochondrial functions in the two cohorts confirmed a modification of respiration etc…. This study provides strong proof of concept of the validity of using iPSC for the modeling of complex diseases. It is the first to use a large scale patient -derived iPSC cohort to uncover important differences in RPE homeostasis associated with geographic atrophy. It clearly identifies mitochondrial activity as a core constitutive difference of the RPE from patients with geographic atrophy, and could be a target of potential therapies for this condition (STACEY/MATT).
Project description:Gigantopithecus blacki was a giant hominid that inhabited Southeast Asia during the Pleistocene. Its evolutionary relationship to other great ape species, and their divergence during the Middle and Late Miocene (16-5.3 Mya), remains disputed. In part, this is due to the absence of cranial and postcranial remains and size-induced allometry. Proposed hypothesis on the phylogenetic positions of Gigantopithecus have therefore been wide-ranging among hominoids, but none has received independent validation based on molecular evidence. To clarify the phylogenetic placement of Gigantopithecus blacki, we retrieved enamel proteome sequences from a 1.9 million years (Mya) old molar found in Chuifeng Cave, China. We demonstrate that Gigantopithecus is most closely related to orangutans (genus Pongo). We also estimate the Gigantopithecus-Pongo divergence to about 10-12 Mya, implying its speciation is part of the Miocene radiation of great apes. These sequences are approximately 6 times older, in a normalized thermal context, than any previously published mammalian proteome or genome. The survival of an Early Pleistocene dental enamel proteome in the subtropics further expands the scope of palaeoproteomic analysis into geographic areas and time periods previously considered incompatible with biomolecular preservation.
Project description:Transcriptome sequencing of non-model organisms is valuable resource of the genetic basis of ecological-meaningful traits. The Royal Irises, Iris section Oncocyclus (Iris: Iridaceae, order Asparagales), are a Middle-East group of species in the course of speciation. The species are characterized with extremely large flowers, a huge range of flower colors and a unique pollination system. The Royal Irises, which are a symbol of conservation in the Middle-east, serve as a model for evolutionary processes of speciation and plant ecology. However, there are not sufficient transcriptomic and genomic data for molecular characterization. Thus, it is necessary to generate massive transcript sequences for functional characterization and molecular marker development for the Royal Irises. The Iris transcriptome sequencing provides valuable resource for studying adaptation-associated traits in this non-model plant. Although intensive eco-evolutionary studies, this is the first reported transcriptome for the Royal Irises. The data available from this study will facilitate gene discovery, functional genomic studies and development of molecular markers in irises, and will provide genetic tools for their conservation.