Project description:This experiment set contains the arrays referenced in Ferea, TL, et al. titled "Systematic changes in gene expression patterns following adaptive evolution in yeast"(Proc Natl Acad Sci USA 1999 96(17):9721-6). A Saccharomyces cerevisiae population was cultured for many generations under conditions to which it is not optimally adapted. These experiments were designed to investigate adaptive evolution under natural selection.
Project description:Model-guided chassis strain design has the potential to accelerate cellfactory development. In this experiment genetic targets were identified in silico and implemented in vivo to design a yeast chassis strain for enhanced production of succinic, malic and fumaric acid. The phenotype of engineered chassis strains was further optimised through adaptive laboratory evolution. RNA-seq analysis of engineered yeast chassis strains, evolved strains and wild-type (CEN.PK background)was performed to determine the effect of engineered gene deletions and evolution on the transcriptome.
Project description:Increased time sampling in an evolve-and-resequence experiment with outcrossing Saccharomyces cerevisiae reveals multiple paths of adaptive change
Project description:Population adaptation to strong selection can occur through the sequential or parallel accumulation of competing beneficial mutations. The dynamics, diversity and rate of fixation of beneficial mutations within and between populations are still poorly understood. To study how the mutational landscape varies across populations during adaptation, we performed experimental evolution on seven parallel populations of Saccharomyces cerevisiae continuously cultured in limiting sulfate medium. By combining qPCR, array CGH, restriction digestion and CHEF gels, and whole genome sequencing, we followed the trajectory of evolution to determine the identity and fate of beneficial mutations. Over a period of 200 generations, the yeast populations displayed parallel evolutionary dynamics that are driven by the coexistence of independent beneficial mutations. Selective amplifications rapidly evolve under this selection pressure, in particular common inverted amplifications containing the sulfate transporter gene SUL1. Compared to single clones, detailed analysis of the populations uncovers a greater complexity whereby multiple subpopulations arise and compete despite a strong selection. The most common evolutionary adaptation to strong selection in these populations grown in sulfate limitation is determined by clonal interference, with adaptive variants both persisting and replacing one another.
Project description:Gene copy-number variation, which provides the raw material for the evolution of novel genes, is surprisingly widespread in natural populations. Experimental evolution studies have demonstrated an extremely high spontaneous rate of origin of gene duplications. When organisms are suboptimally adapted to their environment, gene duplication may compensate for reduced fitness by amplifying promiscuous activity of a gene, or increasing dosage of a suboptimal gene. The overarching goal of this study is to inverstigate whether CNVs constitute a common mechanism of adaptive genetic change during compensatory evolution and to further characterize the role of natural selection in dictating their evolutionary spread at a population-genomic level. Outcrossing populations of C. elegans with low fitness were evolved for >200 generations and the frequencies of CNVs in these populations were analyzed by oligonucleotide array comparative genome hybridization, quantitative PCR, and single-worm PCR. Multiple duplications and deletions were detected in intermediate to high frequencies and several lines of evidence suggest that the changes in frequency were adaptive. 1) Many copy-number changes reached high frequency, were near fixation, or were fixed in a short time. 2) Many independent duplications and deletions in high frequency harbor overlapping regions which likely include genes that are under selection for either higher or lower rates of expression. 3) The size spectrum of deuplications and deletions in the adaptive recovery populations is significantly larger than that of spontaneous copy-number variants in mutation accumulation experiments. This is expected if larger CNVs are more likely to encompass genes that are being selected for altered gene dosage. Out results validate the great potential borne by gene copy-number changes for compensatory evolution and adaptation. Experimental genome evolution of copy-number variants in 25 experimental lines compared to 5 ancestral control lines.
Project description:Adaptive evolution experiment for enhaced tolerance to hydrolysates of lignocellulosic biomass in S. cerevisiae. The samples involves a batch culture in YNB and Hydrolysates. Cells were harvested at mid-exponential phase.
Project description:RNA-seq reads from the outcrossing species Arabidopsis lyrata were produced from flowers to study the consequences of the transition from the ancestral state (outcrossing) to the derived state (selfing) that is observed in the sister species Arabidopsis thaliana. This was done in the context of examining another species pair (Capsella rubella versus Capsella grandiflora, which are selfing and outcrossing, respectively). These samples were generated to complement part of this larger study. Briefly, the shift from outcrossing to selfing is common in flowering plants, but neither the genomic consequences nor the speed with which they appear are well understood. An excellent model for understanding the evolution of self fertilization is provided by Capsella rubella, which became self-compatible <200,000 years ago. We present a reference genome for the species, and compare RNA expression and polymorphism patterns between C. rubella and its outcrossing progenitor C. grandiflora. There is a clear shift in the expression of genes associated with flowering phenotypes; a similar shift is seen in the related genus Arabidopsis, where self-fertilization evolved about 1 million years ago. DNA sequence polymorphisms distinguishing the two Capsella species reveal rapid genome-wide relaxation of purifying selection in C. rubella but without a concomitant change in transposable element abundance. Overall, we document that the transition to selfing may be typified by shifts in expression for genes that function in pollen and flower development, along with a measurable reduction of purifying selection.