Unknown,Transcriptomics,Genomics,Proteomics

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Selection of epigenetic variation in Arabidopsis [SNP data]

ABSTRACT: In Arabidopsis thaliana a high rate of spontaneous epigenetic variation can occur in the DNA methylome in the absence of genetic variation and selection. It has been of great interest, whether natural epigenetic variation is subject to selection and contributes to fitness and adaptation in selective environments. We compared the variation in selected phenotypic traits, genome-wide cytosine DNA methylation and gene expression in two Arabidopsis recombinant inbred lines, which had undergone five generations of selection in experimental landscapes relative to their genetically identical ancestors. Selected populations exerted significant differences in flowering time and the number of branches and fruits, differences that were maintained over two to three generations in the absence of selection. We identified 4,629 and 5,158 differentially methylated cytosines which were overrepresented in genes that regulate flowering time, epigenetic processes, development and morphogenesis. Differentially methylated genes were enriched in differentially expressed genes. Thus, epigenetic variation is subject to selection and may play an important role in the adaptive response of populations in rapidly changing natural environments. Genomic DNA was extracted from whole-plant above-ground tissue of individual 25-day-old plants with the Qiagen DNeasy kit (Qiagen). DNA from two randomly chosen CVL39 individuals from ancestral (A3) lines and from 7 selected (S3) lines that had experienced 5 generations of selection in the three replicated dynamic landscapes (2xD1, 3xD5,2xD6) was sequenced (paired-end, 100 bp) using the Illumina Highseq 2000 Instrument. Single nucleotide polymorphisms and TE insertions were mapped with respect to the recombinant reference genome and compared between selected and ancestral lines.

ORGANISM(S): Arabidopsis thaliana

SUBMITTER: Christian Heichinger

PROVIDER: E-GEOD-47490 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:One of the central goals of evolutionary biology is to explain and predict the molecular basis of adaptive evolution. We studied the evolution of genetic networks in Saccharomyces cerevisiae (budding yeast) populations propagated for more than 200 generations in different nitrogen-limiting conditions. We find that rapid adaptive evolution in nitrogen-poor environments is dominated by the de novo generation and selection of copy number variants (CNVs), a large fraction of which contain genes encoding specific nitrogen transporters including PUT4, DUR3 and DAL4. The large fitness increases associated with these alleles limits the genetic heterogeneity of adapting populations even in environments with multiple nitrogen sources. Complete identification of acquired point mutations, in individual lineages and entire populations, identified heterogeneity at the level of genetic loci but common themes at the level of functional modules, including genes controlling phosphatidylinositol-3-phosphate metabolism and vacuole biogenesis. Adaptive strategies shared with other nutrient-limited environments point to selection of genetic variation in the TORC1 and Ras/PKA signaling pathways as a general mechanism underlying improved growth in nutrient-limited environments. Within a single population we observed the repeated independent selection of a multi-locus genotype, comprised of the functionally related genes GAT1, MEP2 and LST4. By studying the fitness of individual alleles, and their combination, as well as the evolutionary history of the evolving population, we find that the order in which these mutations are acquired is constrained by epistasis. The identification of repeatedly selected variation at functionally related loci that interact epistatically suggests that gene network polymorphisms (GNPs) may be a frequent outcome of adaptive evolution. Our results provide insight into the mechanistic basis by which cells adapt to nutrient-limited environments and suggest that knowledge of the selective environment and the regulatory mechanisms important for growth and survival in that environment greatly increases the predictability of adaptive evolution. mRNA from each evolved clone or from the ancestral strain growing in the specificied nitrogen-limited condition was co-hybridized with mRNA from the ancestral strain grown in ammonium limited media

Project description:We carried out a five-generation selection experiment in which two Arabidopsis accessions (Ler and Cvi) and 17 Recombinant Inbred Lines (RILs) derived from them were subjected in 24 replicated populations to four levels of micro-landscape fragmentation and two levels of disturbance, factorially crossed with each other to yield 8 experimental selection regimes. We used 19 lines (including the two parental Ler and Cvi) in generation 1 of our experiment, nine of which contained the erecta mutation and ten of which did not. Lines expressing the erecta mutation are short and compact and are likely to disperse seeds over shorter distances. Both the non-erecta and the erecta lines spanned the full available range of seed sizes from the original 162 RILs in the collection. We set up 24 experimental landscapes consisting of 2, 4, 8, or 16 patches where the total area was constrained to be equal. Plants that germinated outside the designated suitable patches were removed. In half of the landscapes which we termed static the top 2-3 mm of seeds and soil were removed from the surface of the suitable patches after 8 weeks of growth and reproduction. In the other half of the landscapes which we termed dynamic a number of Petri dishes, equivalent in size and number to the existing suitable patches, were distributed around the landscape at random, to catch dispersing seeds. The seeds collected by these two methods were cold-treated for one week while all patches were replenished with fresh substrate. Seeds were then returned to the surface of the new patches at the beginning of the next generation. Thus, in dynamic landscapes, seeds must disperse to have any chance of entering the next generation, while in static landscapes, only seeds that do not disperse have any chance of further propagation. After five generations of such selection, a single pod from approximately 70 individuals from each landscape was removed. Single individuals derived from such pods were reared under standardized conditions to measure several phenotypic characters, such as seed mass, height, presence of the erecta mutation, flowering time etc. Clear phenotypic differences are apparent between the different landscapes. However, we have no information as to the underlying genes, which might have been selected or the epigenetic modifications that might have occurred. Material for DNA extraction from each population (? 50 plants/population) was collected for subsequent genetic analyses. The allele frequencies of Ler and Cvi alleles was determined at the genome-wide level using ATH1 Affymetrix GeneChips® (each in quadruplicate = 8 parental microarrays). 26638 single feature polymorphisms (SFPs) between these two accessions could be detected. The relative contribution of Ler and Cvi alleles in a population at each locus, for which a single feature polymorphism can be detected, was assessed. We then analyzed the DNA isolated from the experimental populations (24 landscapes of generation 5 = 24 microarrays & original populations in triplicate = 3 microarrays) and determine the relative contributions of Ler and Cvi alleles for the 26638 identified SFPs (i.e. allele frequency shifts).

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Selection of epigenetic variation in Arabidopsis [SNP data]

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