Project description:Environmental stress-induced transgenerational epigenetic effects have been observed in various model organisms and human. The capacity and mechanism of such phenomena, particularly in animals, are poorly understood. In C. elegans, siRNA mediates transgenerational gene silencing through the germline nuclear RNAi pathway. At the organismal level, this pathway plays a transgenerational role in maintaining the germline immortality when C. elegans is under a mild heat stress. However, the underlying molecular mechanism is unknown. In this study, we performed a 12-generation temperature-shift experiment (15˚C->23˚C->15˚C) using the wild type (N2) and a mutant strain that lacks the germline-specific nuclear AGO protein HRDE-1/WAGO-9. We found that the temperature-sensitive mortal germline (Mrt) phenotype of the hrde-1 mutant is reversible, indicating a transgenerational cumulative but also reversible nature of the underlying molecular cause. By taking the whole-genome RNA and chromatin profiling approaches, we revealed an epigenetic role of HRDE-1 in repressing heat stress-induced transcriptional activation of over 280 genes, predominantly in or near LTR retrotransposons. Strikingly, for some of these elements, the heat stress-induced transcription becomes progressively activated in the hrde-1 mutant over several generations under heat stress. Furthermore, the effect of heat stress-induced transcription activation is heritable for at least two generations after the heat stress. Interestingly, the siRNA expression of these genes tend to be heat-inducible in the wild type animals, but not in the hrde-1 mutant, suggesting a role of siRNAs in repressing heat-inducible elements. Our study revealed a novel phenomenon of transgenerational feed-forward transcriptional activation, which is normally repressed in the wild type C. elegans by the germline nuclear RNAi pathway. It also provides a new paradigm to study epigenetic circuitry that connects the environment and gene regulation in the germline.
Project description:Environmental stress-induced transgenerational epigenetic effects have been observed in various model organisms and human. The capacity and mechanism of such phenomena, particularly in animals, are poorly understood. In C. elegans, siRNA mediates transgenerational gene silencing through the germline nuclear RNAi pathway. At the organismal level, this pathway plays a transgenerational role in maintaining the germline immortality when C. elegans is under a mild heat stress. However, the underlying molecular mechanism is unknown. In this study, we performed a 12-generation temperature-shift experiment (15˚C->23˚C->15˚C) using the wild type (N2) and a mutant strain that lacks the germline-specific nuclear AGO protein HRDE-1/WAGO-9. We found that the temperature-sensitive mortal germline (Mrt) phenotype of the hrde-1 mutant is reversible, indicating a transgenerational cumulative but also reversible nature of the underlying molecular cause. By taking the whole-genome RNA and chromatin profiling approaches, we revealed an epigenetic role of HRDE-1 in repressing heat stress-induced transcriptional activation of over 280 genes, predominantly in or near LTR retrotransposons. Strikingly, for some of these elements, the heat stress-induced transcription becomes progressively activated in the hrde-1 mutant over several generations under heat stress. Furthermore, the effect of heat stress-induced transcription activation is heritable for at least two generations after the heat stress. Interestingly, the siRNA expression of these genes tend to be heat-inducible in the wild type animals, but not in the hrde-1 mutant, suggesting a role of siRNAs in repressing heat-inducible elements. Our study revealed a novel phenomenon of transgenerational feed-forward transcriptional activation, which is normally repressed in the wild type C. elegans by the germline nuclear RNAi pathway. It also provides a new paradigm to study epigenetic circuitry that connects the environment and gene regulation in the germline.
Project description:Environmental stress-induced transgenerational epigenetic effects have been observed in various model organisms and human. The capacity and mechanism of such phenomena, particularly in animals, are poorly understood. In C. elegans, siRNA mediates transgenerational gene silencing through the germline nuclear RNAi pathway. At the organismal level, this pathway plays a transgenerational role in maintaining the germline immortality when C. elegans is under a mild heat stress. However, the underlying molecular mechanism is unknown. In this study, we performed a 12-generation temperature-shift experiment (15˚C->23˚C->15˚C) using the wild type (N2) and a mutant strain that lacks the germline-specific nuclear AGO protein HRDE-1/WAGO-9. We found that the temperature-sensitive mortal germline (Mrt) phenotype of the hrde-1 mutant is reversible, indicating a transgenerational cumulative but also reversible nature of the underlying molecular cause. By taking the whole-genome RNA and chromatin profiling approaches, we revealed an epigenetic role of HRDE-1 in repressing heat stress-induced transcriptional activation of over 280 genes, predominantly in or near LTR retrotransposons. Strikingly, for some of these elements, the heat stress-induced transcription becomes progressively activated in the hrde-1 mutant over several generations under heat stress. Furthermore, the effect of heat stress-induced transcription activation is heritable for at least two generations after the heat stress. Interestingly, the siRNA expression of these genes tend to be heat-inducible in the wild type animals, but not in the hrde-1 mutant, suggesting a role of siRNAs in repressing heat-inducible elements. Our study revealed a novel phenomenon of transgenerational feed-forward transcriptional activation, which is normally repressed in the wild type C. elegans by the germline nuclear RNAi pathway. It also provides a new paradigm to study epigenetic circuitry that connects the environment and gene regulation in the germline.
Project description:Heat stress is a major limiting factor for grain yield and grain quality in wheat production. In crops, abiotic stresses have transgenerational effects and the mechanistic basis of stress memory is associated with epigenetic regulation. The current study presents the first systematic analysis of the transgenerational effects of post-anthesis heat stress in tetraploid wheat. Genotype-dependent response patterns to parental and progeny heat stress were found for the leaf physiological traits, harvest components, and grain quality traits measured. Parental heat stress had positive influence on the offspring under re-occurring stress for traits like chlorophyll content, grain weight, grain number and grain total starch content. Integrated sequencing analysis of the small RNAome, mRNA transcriptome, and mRNA degradome provided the first description of the molecular networks mediating heat stress adaption under transgenerational influence. The expression profile of 1771 microRNAs (733 being novel) and 66,559 genes was provided, with differentially expressed microRNAs and genes identified subject to the progeny treatment, parental treatment and tissue type factors. Gene Ontology and KEGG pathway annotation of stress responsive microRNAs-mRNA modules provided further information on their functional roles in biological processes like hormone homeostasis, signal transduction, and protein stabilization. Our results provide new sights on the molecular basis of transgenerational heat stress adaptation, which can be used for improving thermos-tolerance in breeding.
Project description:Plants often experience recurrent stressful events, for example during heat waves. They can adapt to such recurrent heat stress (HS), allowing subsequent survival of more severe HS conditions. At certain genes HS induces sustained expression for several days beyond the actual HS. This transcriptional memory is associated with hyper-methylation of histone H3 lysine 4 (H3K4me3), however, how this is maintained for extended periods of time is unclear. Here, we determined histone turnover by measuring chromatin association of a HS-induced histone H3.3. Genome-wide Histone turnover was not homogenous, in particular, H3.3 was retained longer at HS memory genes compared to HS-induced non-memory genes during the memory phase. While low nucleosome turnover retained H3K4 methylation, its loss did not affect turnover, suggesting that low nucleosome turnover sustains H3K4 methylation (and not vice versa). Together, our results unveil the modulation of histone turnover as a mechanism to retain environmentally-mediated epigenetic modifications.
Project description:This SuperSeries is composed of the following subset Series: GSE25895: Paternally-induced transgenerational environmental reprogramming of metabolic gene expression in mammals (dye swap) GSE25896: Paternally-induced transgenerational environmental reprogramming of metabolic gene expression in mammals (Affymetrix) GSE25897: Paternally-induced transgenerational environmental reprogramming of metabolic gene expression in mammals (small RNA) GSE25898: Paternally-induced transgenerational environmental reprogramming of metabolic gene expression in mammals (meDIP) Refer to individual Series