Project description:At critically short telomeres TERRA RNA-DNA hybrids become stabilized and drive homology-directed repair (HDR) to delay replicative senescence. However, even at long- and intermediate-length telomeres, not subject to HDR, transient TERRA RNA-DNA hybrids form, suggestive of additional roles. Here, we report that hybrids at telomeres prevent resection by the Exo1 nuclease when telomeres become non-functional. We employed the well-characterized cdc13-1 allele, where telomere resection can be induced in a temperature dependent manner, to demonstrate that ssDNA generation at telomeres is either prevented or augmented when RNA-DNA hybrids are stabilized or destabilized, respectively. The viability of cdc13-1 cells is affected by the presence or absence of hybrids accordingly. These results give insights into an additional role of TERRA at dysfunctional telomeres suggesting that it not only affects replicative senescence rates through HDR activation at critically short telomeres, but may also affect resection rates at intermediate length telomeres in pre-senescent cells.
Project description:The heterotic hybrid offspring of Arabidopsis accessions C24 and Landsberg erecta have altered methylomes. Changes occur most frequently at loci where parental methylation levels are different. There are context-specific biases in the non-additive methylation patterns with mCG generally increased and mCHH decreased relative to the parents. These changes are a result of two main mechanisms, Trans Chromosomal Methylation (TCM) and Trans Chromosomal deMethylation (TCdM), where the methylation level of one parental allele alters to resemble that of the other parent. Regions of altered methylation are enriched around genic regions and are often correlated with changes in siRNA levels. We identified examples of genes with altered expression likely to be due to methylation changes and suggest that in crosses between the C24 and Ler accessions, epigenetic controls can be important in the generation of altered transcription levels which may contribute to the increased biomass of the hybrids. C24, Ler, and C24 x Ler
Project description:Hybrid progeny can enjoy increased fitness and stress tolerance relative to their ancestral species, a phenomenon known as hybrid vigor. Though this phenomenon has been documented throughout the Eukarya, evolution of hybrid populations has yet to be explored experimentally in the lab. To fill this knowledge gap we created a pool of Saccharomyces cerevisiae and S. bayanus homoploid and aneuploid hybrids, and then investigated how selection in the form of incrementally increased temperature or ethanol impacted hybrid genome structure and adaptation. During 500 generations of continuous ammonia-limited, glucose-sufficient culture, temperature was raised from 25C to 46??C. This selection invariably resulted in nearly-complete loss of the S. bayanus genome, although the dynamics of genome loss differed among independent replicates. Temperature-evolved isolates were significantly more thermal tolerant and exhibited greater phenotypic plasticity than parental species and founding hybrids. By contrast, when the same hybrid pool was subjected to increases in exogenous ethanol from 0% to 14%, selection favored euploid S. cerevisiae x S. bayanus hybrids. Ethanol-evolved isolates exhibited significantly greater ethanol tolerance relative only to S. bayanus and one of the founding hybrids tested. Adaptation to thermal and ethanol stress manifested as heritable changes in cell wall structure demonstrated by resistance to zymolyase or micafungin treatment. This is the first study to show experimentally that the fate of interspecific hybrids critically depends on the type of selection they encounter during the course of evolution. Array-CGH was performed on the S. cerevisiae parent strain CEN.PK (GSY2160), the S. bayanus parent strain CBS7001 (GSY2161) and on the F1 interspecific hybrid resulting from mating the 2 parents (GSY2168). Additionally, three rare viable spores obtained after sporulation of the F1 were assayed by array-CGH (F2a, F2b, F2c). A large pool of F2 spores (and probably some number of F1 hybrid cells) were subjected to gradually increasing temperatures, in three independent vessels, with populations sampled at various generation times. Likewise, the same pool was used to found populations in an additional three independent vessels, which were then subjected to gradually increasing ethanol concentrations (at constant temperature). Array-CGH was performed on three different clones from each of the three temperature vessels at the final 500 generation time point (T500 clones). Biological replicates of the T500 clones were performed (T500-new). Two self-self array-CGH hybridization controls were also performed (self-control). Array-CGH was performed on one clone from each of the three ethanol vessels taken at the 400 generation timepoint (EtOH400gen clones).
Project description:Hybrid generations usually face either a heterosis advantage or a breakdown that can be expressed by the level of parasite infection in hybrid hosts. Hybrids are less infected by parasites than parental species (especially F1 generations) or more infected than parental species (especially post-F1 generations). We performed the experiment with blood-feeding gill parasite Paradiplozoon homoion (Monogenea) infecting leuciscid species, Abramis brama and Rutilus rutilus, their F1 generation, and two backcross generations. Backcross generations tended to be more parasitized than parental lines and the F1 generation. The number of differentially expressed genes (DEGs) was lower in F1 hybrids and higher in backcross hybrids when compared to each of the parental lines. The main groups of DEGs were shared among lines, however, Abramis brama and Rutilus rutilus differed in some of the top gene ontology (GO) terms. DEG analyses revealed the role of heme binding and erythrocyte differentiation after infection by blood-feeding P. homoion. Two backcross generations shared some of the top GO terms representing mostly downregulated genes associated with P. homoion infection. KEGG analysis revealed the importance of disease-associated pathways. The majority of them were shared by two backcross generations. Our study revealed the most pronounced DEGs associated with monogenean infection in backcross hybrids, potentially explained by hybrid breakdown. The gene expression of F1 hybrids was little affected by P. homoion, suggesting the hybrid advantage.
Project description:MiRNA expression profiling on 14.5 day old testis from sterile (PWD x B6)F1, (PWK x B6)F1 and fertile (B6 x PWD)F1 inter-subspecific hybrids were performed to study the genome wide variation in miRNA expression between different inter-subspecific hybrids during meiosis.
Project description:Hybrid progeny can enjoy increased fitness and stress tolerance relative to their ancestral species, a phenomenon known as hybrid vigor. Though this phenomenon has been documented throughout the Eukarya, evolution of hybrid populations has yet to be explored experimentally in the lab. To fill this knowledge gap we created a pool of Saccharomyces cerevisiae and S. bayanus homoploid and aneuploid hybrids, and then investigated how selection in the form of incrementally increased temperature or ethanol impacted hybrid genome structure and adaptation. During 500 generations of continuous ammonia-limited, glucose-sufficient culture, temperature was raised from 25C to 46??C. This selection invariably resulted in nearly-complete loss of the S. bayanus genome, although the dynamics of genome loss differed among independent replicates. Temperature-evolved isolates were significantly more thermal tolerant and exhibited greater phenotypic plasticity than parental species and founding hybrids. By contrast, when the same hybrid pool was subjected to increases in exogenous ethanol from 0% to 14%, selection favored euploid S. cerevisiae x S. bayanus hybrids. Ethanol-evolved isolates exhibited significantly greater ethanol tolerance relative only to S. bayanus and one of the founding hybrids tested. Adaptation to thermal and ethanol stress manifested as heritable changes in cell wall structure demonstrated by resistance to zymolyase or micafungin treatment. This is the first study to show experimentally that the fate of interspecific hybrids critically depends on the type of selection they encounter during the course of evolution.
Project description:This SuperSeries is composed of the following subset Series: GSE34655: Genome-wide profiling of DNA methylation in two Arabidopsis ecotypes and their reciprocal hybrids - mRNA-seq GSE34656: Genome-wide profiling of DNA methylation in two Arabidopsis ecotypes and their reciprocal hybrids - small RNA-seq GSE34657: Genome-wide profiling of DNA methylation in two Arabidopsis ecotypes and their reciprocal hybrids - Bisulfite-seq Refer to individual Series
Project description:The behavior of transcriptomes and epigenomes in hybrids of heterotic parents is of fundamental interest. Here we report highly integrated maps of the epigenome, mRNA and small RNA transcriptomes of two rice subspecies and their reciprocal hybrids. We found that gene activity was correlated with DNA methylation and both active and repressive histone modifications in transcribed regions. Differential epigenetic modifications correlated with changes in transcript levels among hybrids and parental lines. Distinct patterns in gene expression and epigenetic modifications in reciprocal hybrids were observed. Through analyses of single nucleotide polymorphisms from our sequence data, we observed a high correlation of allelic bias of epigenetic modifications or gene expression in reciprocal hybrids with their differences in the parental lines. The abundance of distinct small RNA size classes differed between the parents and more small RNAs were down-regulated than up-regulated in the reciprocal hybrids. Together, our data reveals a comprehensive overview of transcriptional and epigenetic trends in heterotic rice crosses, and provides a very useful resource for the rice community.