Project description:Chromatin accessibility is an important functional genomics phenotype that influences transcription factor binding and gene expression. Genome-scale technologies allow chromatin accessibility to be mapped with high-resolution, facilitating detailed analyses into the genetic architecture and evolution of chromatin structure within and between species. We performed Formaldehyde-Assisted Isolation of Regulatory Elements sequencing (FAIRE-Seq) to map chromatin accessibility in two parental haploid yeast species, Saccharomyces cerevisiae and Saccharomyces paradoxus and their diploid hybrid. We show that although broad-scale characteristics of the chromatin landscape are well conserved between these species, accessibility is significantly different for 947 regions upstream of genes that are enriched for GO terms such as intracellular transport and protein localization exhibit. We also develop new statistical methods to investigate the genetic architecture of variation in chromatin accessibility between species, and find that cis effects are more common and of greater magnitude than trans effects. Interestingly, we find that cis and trans effects at individual genes are often negatively correlated, suggesting widespread compensatory evolution to stabilize levels of chromatin accessibility. Finally, we demonstrate that the relationship between chromatin accessibility and gene expression levels is complex, and a significant proportion of differences in chromatin accessibility might be functionally benign. There are 20 samples in total. These consist of 10 FAIRE-seq samples, specifically 6 haploid samples, S. cerevisiae strain UWOPS05_217_3 replicates 1 and 2, S. cerevisiae strain DBVPG1373 replicates 1 and 2, and S. paradoxus strain CBS432 replicates 1 and 2. There are also 4 diploid hybrid samples, hybrid between S. cerevisiae strain UWOPS05_217_3 and S. paradoxus strain CBS432 replicates 1 and 2, and the hybrid between S. cerevisiae strain DBVPG1373 and S. paradoxus strain CBS432 replicates 1 and 2. There are also RNA-seq samples for each of these 10 samples.
Project description:Chromatin accessibility is an important functional genomics phenotype that influences transcription factor binding and gene expression. Genome-scale technologies allow chromatin accessibility to be mapped with high-resolution, facilitating detailed analyses into the genetic architecture and evolution of chromatin structure within and between species. We performed Formaldehyde-Assisted Isolation of Regulatory Elements sequencing (FAIRE-Seq) to map chromatin accessibility in two parental haploid yeast species, Saccharomyces cerevisiae and Saccharomyces paradoxus and their diploid hybrid. We show that although broad-scale characteristics of the chromatin landscape are well conserved between these species, accessibility is significantly different for 947 regions upstream of genes that are enriched for GO terms such as intracellular transport and protein localization exhibit. We also develop new statistical methods to investigate the genetic architecture of variation in chromatin accessibility between species, and find that cis effects are more common and of greater magnitude than trans effects. Interestingly, we find that cis and trans effects at individual genes are often negatively correlated, suggesting widespread compensatory evolution to stabilize levels of chromatin accessibility. Finally, we demonstrate that the relationship between chromatin accessibility and gene expression levels is complex, and a significant proportion of differences in chromatin accessibility might be functionally benign.
Project description:The depiction of maize chromatin architecture using Assay for Transposase Accessible Chromatin with high-throughput sequencing (ATAC-seq) provides great opportunities to investigate cis-regulatory elements, which is crucial for crop improvement. We demonstrate a streamlined ATAC-seq protocol for maize in which nuclei purification can be achieved without cell sorting, and using only a standard bench-top centrifuge. Our protocol, coupled with the bioinformatic analysis, provides a precise and efficient assessment of the maize chromatin landscape.
Project description:An understanding of how genetic variants affect chromatin accessibility in unique cellular context remains poorly understood. Here, we generated single-cell chromatin accessibility profiles in nearly 200 diverse maize inbred lines, revealing for the first time variants that affect chromatin accessibility in distinct cellular contexts.
Project description:Gene expression and complex phenotypes are determined by the activity of cis-regulatory elements. However, an understanding of how extant genetic variants affect cis-regulatory activity remains limited. Here, we investigated the consequences of cis-regulatory diversity using single-cell genomics of >0.7 million nuclei across 172 maize inbreds. Our analyses pinpointed cis-regulatory elements distinct to domesticated maize and how transposons rewired the regulatory landscape. We found widespread chromatin accessibility variation associated with >4.6 million genetic variants with largely cell-type-specific effects. Variants in TEOSINTE BRANCHED1/CYCLOIDEA/PROLIFERATING CELL FACTOR binding sites were the most prevalent determinants of chromatin accessibility. Finally, integration of genetic variants associated with chromatin accessibility, organismal trait variation, and population differentiation revealed how local adaptation has rewired regulatory networks in unique cellular context to alter maize flowering phenotypes.
Project description:Maize (Zea mays) is one of the most important crop in the world. Better understanding the maize chromatin architecture points to novel approaches to improve crop yield. Here, we describe the first ATAC-seq protocol to assess the maize genome. Fresh leaf tissue was gently chopped by a blade to release intact nuclei which later were fractionated using Percoll-sucrose gradient. The isolated nuclei were treated with a transposase that fragments and tags the genome; these fragments were subjected to two rounds of PCR to generate the ATAC-seq library. In the first round of PCR, these fragments were amplified with 5 cycles and sequencing barcodes were added. A fraction of the first PCR product was subjected to qPCR to determine the optimal amplification cycle number in the second round of PCR. The library quality can be assessed by a Bioanalyzer prior to sequencing. The distinct bands indicated good quality. After sequencing, the computational analysis of fragment size distribution may show patterns of periodicity that is a characteristic to ATAC-seq libraries. In our preliminary analysis, we found that 85% percent of the identified regions deviate from closed regions previously identified by MNase-seq, suggesting that the ATAC-seq library preparation procedure described here is effective in identifying open chromatin regions of the maize genome.
Project description:DNA methylation is one of the most widely distributed epigenetic marks that has a profound impact on developmental regulation, yet its influence on chromatin accessibility and 3D genome architecture is not well explored in plants. Here, we present genome-wide chromatin accessibility profiles of 18 Arabidopsis mutants that are deficient in CG, CHG or CHH DNA methylation. We find that chromatin inaccessibility at heterochromatin regions are maintained by DNA methylation in all three contexts. Many regions maintain their chromatin inaccessibility when DNA methylation is lost in only one or two contexts but we found the most increase in accessibility at sites that shown DNA methylation reduction in all contexts, suggesting an interplay between CG and non-CG methylation and chromatin accessibility. In addition, we observed that an increase in chromatin accessibility is accompanied with chromatin decompaction of many transposable elements, which leads to heterochromatin decompaction and an enhancement of long-range chromosomal interactions in the 3D genome architecture. Together, these results provide a valuable resource for chromatin compaction analyses and uncover a pivotal role for DNA methylation in the maintenance of heterochromatin inaccessibility in Arabidopsis.