Project description:Isogenic, toxin B (tcdB) mutants of two independently isolated erythromycin-sensitive derivatives (630E and 630Δerm) of the Clostridium difficile strain CD630 have previously been shown to behave differently in the hamster model of infection. Those based on strain 630E failed to cause disease, whereas those based on 630Δerm did. Here we show that whilst 630Δerm and its derivatives behave in a comparable way to the parental strain CD630 in terms of growth rate, motility, sporulation, toxin production and virulence, strain 630E and its derivatives do not. They grow more slowly, achieve lower final cell densities, exhibit a reduced capacity for spore formation, express lower levels of toxin and are less virulent in the hamster model. Using Next Generation Sequencing, a total of three SNPs were found that were in both CD630 and 630Δerm. In addition to these, 630Δerm had eight unique SNPs compared to CD630 and 630E, while 630E had 11 SNPs not found in the other two strains. The strain-specific SNPs most likely arose during the repeated subculture experiments undertaken to isolate these ermB deletion strains. The relatively large number of mutations present meant that the identification of those SNPs responsible for the altered properties of 630E was not possible. Allelic exchange was used to correct three mutational changes in 630E, but with essentially no effect on phenotype. These were a 150 bp inversion in the promoter region of a flagella operon, the truncation of CD630_12740 (topoisomerase I), and the correction of a SNP that results in the fusion of two components of a glucose phosphor-transferase-system. To complete the analysis we performed RNAseq, comparing the transcriptome of the three strains at three different time points. The finding corroborated the many differences between the strains, but also highlighted that one SNP cannot necessarily be attributed to one particular expression pattern or even phenotype. In conclusion 630Δerm more accurately mirrors the behaviour of the parental strain CD630, hence if genetic-based studies with C. difficile strain CD630 are necessary, then the use of strain 630∆erm should be favoured over strain 630E. At a fundamental level, our data underlines the importance of effective strain curation and the need to genome re-sequence master seed banks wherever possible.

Project description:Purpose: Water stress limits plant survival and production in many parts of the world. Identification of genes and alleles responding to water stress conditions is important in breeding plants better adapted to drought. Currently there are no studies examining the transcriptome wide gene and allelic expression patterns under water stress conditions. We used RNA sequencing (RNA-seq) to identify the candidate genes and alleles and to explore the evolutionary signatures of selection Methods: We studied the effect of water stress on gene expression in Eucalyptus camaldulensis seedlings derived from three natural populations. We used reference-guided transcriptome mapping to study gene expression. Reads mapping to predicted transcripts were analysed with edgeR pacakge to study differntial expression of genes under control and water-stress conditions. SNPs within the genes were obtained using pileup file generated with samtools and the SNP frequencies were analysed with VarScan package. SNPs were further characterised as sysnonymous and non-synonymous using popoolation2 pacakge. Results: Several genes showed differential expression between control and stress conditions. Gene ontology (GO) enrichment tests revealed up-regulation of 140 stress-related gene categories and down-regulation of 35 metabolic and cell wall organisation gene categories. More than 190,000 single nucleotide polymorphisms (SNPs) were detected and 2737 of these showed differential allelic expression. Allelic expression of 52% of these variants was correlated with total gene expression. Signatures of selection patterns were studied by estimating the proportion of nonsynonymous to synonymous substitution rates (Ka/Ks). The average Ka/Ks ratio among the 13,719 genes was 0.39 indicating that most of the genes are under purifying selection. Among the positively selected genes (Ka/Ks > 1.5) apoptosis and cell death categories were enriched. Of the positively selected genes, ninety genes showed differential expression and 27 SNPs from 17 positively selected genes showed differential allelic expression between treatments. Conclusions: Correlation of allelic expression of several SNPs with total gene expression indicates that these variants may be the cis-acting variants or in linkage disequilibrium with such variants. Enrichment of apoptosis and cell death gene categories among the positively selected genes reveals the past selection pressures experienced by the populations used in this study. Leaf mRNA of 12 samples were used to study the gene expression under control and water-stress conditions. Three samples under water-stress conditions and three samples under control conditions were used as biological replicates for differenctial gene expression between the treatments. High-throughput sequence reads from mRNA samples were generated by deep sequencing with Illumina GAIIx.

Project description:Purpose: Water stress limits plant survival and production in many parts of the world. Identification of genes and alleles responding to water stress conditions is important in breeding plants better adapted to drought. Currently there are no studies examining the transcriptome wide gene and allelic expression patterns under water stress conditions. We used RNA sequencing (RNA-seq) to identify the candidate genes and alleles and to explore the evolutionary signatures of selection Methods: We studied the effect of water stress on gene expression in Eucalyptus camaldulensis seedlings derived from three natural populations. We used reference-guided transcriptome mapping to study gene expression. Reads mapping to predicted transcripts were analysed with edgeR pacakge to study differntial expression of genes under control and water-stress conditions. SNPs within the genes were obtained using pileup file generated with samtools and the SNP frequencies were analysed with VarScan package. SNPs were further characterised as sysnonymous and non-synonymous using popoolation2 pacakge. Results: Several genes showed differential expression between control and stress conditions. Gene ontology (GO) enrichment tests revealed up-regulation of 140 stress-related gene categories and down-regulation of 35 metabolic and cell wall organisation gene categories. More than 190,000 single nucleotide polymorphisms (SNPs) were detected and 2737 of these showed differential allelic expression. Allelic expression of 52% of these variants was correlated with total gene expression. Signatures of selection patterns were studied by estimating the proportion of nonsynonymous to synonymous substitution rates (Ka/Ks). The average Ka/Ks ratio among the 13,719 genes was 0.39 indicating that most of the genes are under purifying selection. Among the positively selected genes (Ka/Ks > 1.5) apoptosis and cell death categories were enriched. Of the positively selected genes, ninety genes showed differential expression and 27 SNPs from 17 positively selected genes showed differential allelic expression between treatments. Conclusions: Correlation of allelic expression of several SNPs with total gene expression indicates that these variants may be the cis-acting variants or in linkage disequilibrium with such variants. Enrichment of apoptosis and cell death gene categories among the positively selected genes reveals the past selection pressures experienced by the populations used in this study.

Project description:ChIP-seq has become the method of choice for studying functional DNA-protein interactions on a genome wide scale. The method is based on co-immunoprecipitation of DNA binding proteins with formaldehyde cross-linked DNA, followed by deep sequencing of immunoprecipitated chromatin fragments, allowing for the identification of binding sites with high accuracy [1-5]. Traditionally, genome-wide tiling path microarrays were used for the detection of specifically immunoprecipitated DNA fragments, but current next-generation sequencers now generate sufficient data to assay multiple samples in a single sequencing run, making this method more time and cost effective compared to microarray-based approaches [2]. However, due to limitations in read length of next generation sequencing technologies (50-76bp), it is not possible to sequence the complete length of immunoprecipitated DNA fragments which can be up to 2kb long reflecting biology in case of big protein complexes. As a consequence only the ends of the immunoprecipitated DNA fragments are sequenced. Deconvolution of sequencing reads mapping to the positive and negative strand is required to identify the real DNA binding site [4-9]. This limitation is most obvious in case of large complex regions where multiple binding sites of various regulatory elements are clustered close to each other. Deconvolution of such regions and the exact identification of individual binding positions is very challenging [4]. Similar problems can occur when studying histone positioning in cases where the length of ChIP fragments is bigger than the average distance of 2 neighboring nucleosomes. In addition frequently only narrow size range of immunoprecipitated fragments is selected for sequencing and thus possible bias towards binding regions within the selected range can be expected by loosing larger fragments possible originated from protein complexes interacting with DNA. To circumvent these complications, we modified the procedure for the preparation of ChIP-seq samples by introducing an additional extensive fragmentation round after isolation of immunoprecipitated chromatin to generate 70-110 bp long DNA fragments. For testing, we choose Tcf4 protein which is a well-studied downstream element of the Wnt-pathway for which the genome wide binding site profile is known was already known from ChIP-on-CHIP experiments [10]. Using the modified approach, we were able to identify Tcf4 binding sites at near nucleotide resolution without computational deconvolution. Furthermore, high-resolution information on genome-wide binding site regions allowed for the identification of potential novel Tcf4 co-factors as well as target genes. 5 samples + 3 input samples

			Action	DRS
	BJE-1-diploid.vcf.gz	Vcf
	BJE-1-diploid.vcf.gz.tbi	Vcf
	BJE-2-diploid.vcf.gz	Vcf
	BJE-2-diploid.vcf.gz.tbi	Vcf
	BJE-3-diploid.vcf.gz	Vcf

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Development of single nucleotide polymorphisms for Brassica juncea

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