ABSTRACT: Synonymous genetic variation in natural isolates of Escherichia coli does not predict where synonymous substitutions occur in a long-term experiment
Project description:Previous work has demonstrated that non-synonymous mutations in the gene encoding the putative transcription factor CpMrr1 can influence fluconazole susceptibility; however, the direct contribution of these mutations and how they influence fluconazole resistance in clinical isolates is poorly understood. We identified ten non-synonymous CpMRR1 mutations in a collection of 35 fluconazole resistant clinical isolates. The mutations leading to the A854V, R479K, and I283R substitutions were further examined and found to be activating mutations leading to increased fluconazole resistance. In addition to CpMDR1, we identified another major facilitator superfamily (MFS) transporter gene (CpMDR1B, CPAR2_603010) and an ATP-binding Cassette (ABC) transporter gene (CpCDR1B, CPAR2_304370), as being up-regulated in isolates carrying CpMRR1 activating mutations.
Project description:Gene expression is regulated both by cis elements, which are DNA segments closely linked to the genes they regulate, and by trans activating factors, which are usually proteins capable of diffusing to unlinked genes. Understanding the patterns and sources of regulatory variation is crucial for understanding phenotypic and genome evolution. Here, we investigate the global patterns of gene expression evolution in Saccharomyces cerivisiae. We report statistical methods useful in quantifying cis and trans regulation using next generation sequencing data. Using these methods, measured genome-wide allele-specific expression by deep sequencing to investigate the genetic architecture of gene regulatory variation between two strains of Saccharomyces cerevisiae. We find that expression polymorphism in yeast is common for both cis and trans regulation, though trans variation is more common. Our detailed analyses of the effects of functional constraint on expression variation as indicated by measures such as protein connectivity, gene essentiality, and the ratio of nonsynonymous substitutions to synonymous substitutions clearly reveal that both classes of variation are under purifying selection, but trans variation is more sensitive to selective constraint. Comparing interspecific expression divergence between S. cerevisiae and S. paradoxus to our intraspecific variation suggests that natural selection strongly influences the patterns of variation we observe. Further analyses revealed that cis divergence is more frequently mediated by positive Darwinian selection than trans divergence, which is compatible with neutral evolution. Study the gene expression patterns in two strains of yeast (BY and RM)
Project description:Gene expression is regulated both by cis elements, which are DNA segments closely linked to the genes they regulate, and by trans activating factors, which are usually proteins capable of diffusing to unlinked genes. Understanding the patterns and sources of regulatory variation is crucial for understanding phenotypic and genome evolution. Here, we investigate the global patterns of gene expression evolution in Saccharomyces cerivisiae. We report statistical methods useful in quantifying cis and trans regulation using next generation sequencing data. Using these methods, measured genome-wide allele-specific expression by deep sequencing to investigate the genetic architecture of gene regulatory variation between two strains of Saccharomyces cerevisiae. We find that expression polymorphism in yeast is common for both cis and trans regulation, though trans variation is more common. Our detailed analyses of the effects of functional constraint on expression variation as indicated by measures such as protein connectivity, gene essentiality, and the ratio of nonsynonymous substitutions to synonymous substitutions clearly reveal that both classes of variation are under purifying selection, but trans variation is more sensitive to selective constraint. Comparing interspecific expression divergence between S. cerevisiae and S. paradoxus to our intraspecific variation suggests that natural selection strongly influences the patterns of variation we observe. Further analyses revealed that cis divergence is more frequently mediated by positive Darwinian selection than trans divergence, which is compatible with neutral evolution.
Project description:Illumina RNA-seq data were generated for nine taxa in Sphagnopsida (Bryophyta). Analyses of frequency plots for synonymous substitutions per synonymous site (Ks) between paralogous gene pairs were conducted to look for signals of large scale or genome-wide duplication events in each transcriptome. Raw data for four of the nice species studied are provided here. The data for the remaining species are provided elsewhere (see pape for details).