Project description:To examine the rice genome methylation landscape and assess its functional significance, we generated the first single-base resolution genome methylation maps for Oryza sativa ssp. japonica, indica and their wild relatives, Oryza rufipogon and Oryza nivara. The methylation level of rice genomes is four times higher than that of Arabidopsis. Methylation in the promoter and gene body regions have similar patterns and effects on gene expression as those in Arabidopsis but different from a previous study on rice chromosomes 4 and 10. Most interestingly, we discovered for the first time that methylation in gene transcriptional termination regions can significantly repress gene expression, and the effect is even stronger than promoter methylation, which opens a new direction in the study of epigenetic regulation of gene expressions. Through integrated analysis of genetic, methylome and expression variation between cultivated and wild rice, we found that the genetic factor reflected by DNA variations may be the major determinant for methylation patterns at the whole-genome level and that methylation variation can only account for limited expression variation of genes between cultivated and wild rice.
Project description:Lysine crotonylation (Kcr) is a newly discovered post-translational modification (PTM) existing in mammals. A global crotonylome analysis was undertaken in rice (Oryza sativa L. japonica) using high accuracy nano-LC-MS/MS in combination with crotonylated peptide enrichment. A total of 1,265 lysine crotonylation sites were identified on 690 proteins in rice seedlings. Subcellular localization analysis revealed that 51% of the crotonylated proteins identified were localized in chloroplasts. The photosynthesis-associated proteins were also mostly enriched in total crotonylated proteins. In addition, a genomic localization analysis of histone Kcr by ChIP-seq was performed to assess the relevance between histone Kcr and the genome. Of the 10,923 identified peak regions, the majority (86.7%) of the enriched peaks were located in gene body, especially exons. Furthermore, the degree of histone Kcr modification was positively correlated with gene expression in genic regions. Compared with other published histone modification data, the Kcr was co-located with the active histone modifications. Interestingly, histone Kcr facilitated expression of genes with existing active histone modifications. In addition, 77% of histone Kcr modifications overlapped with DNase hypersensitive sites (DHSs) in intergenic regions of the rice genome, and might mark other cis-regulatory DNA elements which are different from IPA1, a transcription activator in rice seedlings. Overall, our results provide a comprehensive understanding of the biological functions of the crotonylome and new active histone modification in transcriptional regulation in plants.
Project description:Lysine crotonylation (Kcr) is a newly discovered post-translational modification (PTM) existing in mammalian. Here, we performed a global crotonylome analysis of rice (Oryza sativa L. japonica) using high accuracy nano-LC-MS/MS in combination with crotonylated peptide enrichment. A total of 1,265 lysine crotonylation sites were identified on 690 proteins in rice seedlings. Subcellular localization analysis revealed that 51% of the crotonylated proteins identified were predicted to be associated with chloroplasts. The photosynthesis-associated proteins were also mostly enriched in total crotonylated proteins. Furthermore, to assess the relevance between histone Kcr and the genome, we performed a genomic localization analysis of histone Kcr by ChIP-seq analysis. Of the 10,923 identified peak regions, the majority (86.7%) of the enriched peaks were located in genes, especially exons. Furthermore, the degree of histone Kcr modification was positively correlated with gene expression in genic regions. Compared with other published histone modification data, the Kcr was co-located with the active histone modifications. Interestingly, histone Kcr facilitated expression of genes with existing active histone modifications. In addition, 77% of histone Kcr modifications overlapped with DNase hypersensitive sites (DHSs) in intergenic regions of the rice genome, and might mark other cis-regulatory DNA elements which are different from IPA1, a transcription activator in rice seedling. Overall, our results provide a comprehensive understanding of the biological functions of the crotonylome and new active histone modification in transcriptional regulation in plants.
Project description:The transcriptional regulatory structure of plant genomes remains poorly defined relative to that of animals. It has been unclear how many cis-regulatory elements generally exist in plant genomes, where these elements lie in relation to their target promoters, and how these features are conserved across species. We employed the Assay for Transposase-Accessible Chromatin with sequencing (ATAC-seq) in four different plant species (Arabidopsis thaliana, Medicago truncatula, Solanum lycopersicum, and Oryza sativa) to delineate open chromatin regions and transcription factor (TF) binding sites across each genome. Despite a ~10-fold variation in intergenic space among species, the majority of open chromatin regions consistently lie within 3 kb upstream of a transcription start site (TSS) in all four species. Nearly 70% of genes in Arabidopsis, Medicago, and Rice have a single putative regulatory region upstream of the TSS, while a similar percentage of tomato genes have 2-5 such elements. Despite variation in the location and number of regulatory elements within orthologous gene sets, transcriptional regulatory networks appear to be largely conserved across species. Profiling of open chromatin in the Arabidopsis root hair and non-hair epidermal cell types indicated that while the open chromatin landscapes of these two cell types were largely indistinguishable on a global scale, thousands of relatively subtle, quantitative cell-specific differences could be found. Analysis of TF binding sites in these differentially accessible regions led to the discovery of a MYB-driven transcriptional regulatory module unique to the hair cell type, which appears to control both hair cell fate regulators and abiotic stress responses. Our cross-species and cross-cell type analyses revealed common transcriptional regulatory principles among species and shed light on the mechanisms that produce cell type-specific transcriptomes during development.
Project description:To examine the rice genome methylation landscape and assess its functional significance, we generated the first single-base resolution genome methylation maps for Oryza sativa ssp. japonica, indica and their wild relatives, Oryza rufipogon and Oryza nivara. The methylation level of rice genomes is four times higher than that of Arabidopsis. Methylation in the promoter and gene body regions have similar patterns and effects on gene expression as those in Arabidopsis but different from a previous study on rice chromosomes 4 and 10. Most interestingly, we discovered for the first time that methylation in gene transcriptional termination regions can significantly repress gene expression, and the effect is even stronger than promoter methylation, which opens a new direction in the study of epigenetic regulation of gene expressions. Through integrated analysis of genetic, methylome and expression variation between cultivated and wild rice, we found that the genetic factor reflected by DNA variations may be the major determinant for methylation patterns at the whole-genome level and that methylation variation can only account for limited expression variation of genes between cultivated and wild rice. A single young panicle from each of the cultivated rice subspecies and the two wild rice species was ground in liquid nitrogen to fine powder using mortar and pestle. Total RNAs were isolated using the RNeasy Plant Mini Kit (Qiagen). DGE-tag libraries were constructed using the DGE-Tag Profiling NlaIII Sample Prep Kit (Illumina) according to the manufacturer's instructions. This submission represents the gene expression component of the study.
Project description:We present evidence for a new level of genome folding, whereby distant domains megabases apart fuse to form meta-domains. Within meta-domains, certain gene promoters pair with structural intergenic elements in the distant TAD. These long-range associations occur in a large fraction of Drosophila neurons, but support transcription in only a subset of cells in the nervous system. Most of the associated genes encode neuronal determinants, including those engaged in axonal guidance and adhesion. We used single cell assay for transposase-accessible chromatin using sequencing (scATAC-seq) to identify regions of open chromatin at single cell resolution.
Project description:Bacteria can generate heterogeneity through phase variation, including enzyme-mediated inversion of specific intergenic regions of genomic DNA. We developed a computation tool that identifies invertible elements using long-read datasets, PhaVa. We identified over 300 ‘intragenic invertons,’ a new class of invertible elements entirely within genes, in both bacteria and archaea. In the gut commensal Bacteroides thetaiotaomicron, we experimentally characterized an intragenic inverton in the thiamine biosynthesis protein thiC. We used mass spectrometry in data-independent acquisition mode to identify and quantify B. theta proteins, including thiC inverton expression at the protein level.