Project description:The genomic sequences of diverse varieties of many crop species continue to be produced at a frenetic pace. However, it remains challenging to develop complete annotations of functional genes and regulatory elements in these genomes. Here, we explore the potential to use DNA methylation profiles to develop more complete and refined annotations. Using leaf tissue in maize, we define ~100,000 unmethylated regions (UMRs) that account for 5.8% of the genome; 33,375 UMRs (1.3% of the genome) are found greater than 2 kilobase pairs from genes. UMRs are highly stable in multiple vegetative tissues and they capture the vast majority of accessible chromatin regions from leaf tissue. However, many UMRs are not accessible in leaf (leaf-iUMRs) and these represent a set of genomic regions with potential to become accessible in specific cell types or developmental stages. Leaf-iUMRs often occur near genes that are expressed in other tissues and are enriched for transcription factor (TF) binding sites of TFs that are also not expressed in leaf tissue. The leaf-iUMRs exhibit unique chromatin modification patterns and are enriched for chromatin interactions with nearby genes. The total UMRs space in four additional monocots ranges from 80-120 megabases, which is remarkably similar considering the range in genome size of 271 megabases to 4.8 gigabases. In summary, based on the profile from a single tissue, DNA methylation signatures pinpoint both accessible regions and regions poised to become accessible or expressed in other tissues. Thus, UMRs can provide powerful filters to distill large genomes down to the small fraction putative functional elements and facilitate the discovery of tens of thousands of novel candidate regulatory regions.
Project description:The genomic sequences of diverse varieties of many crop species continue to be produced at a frenetic pace. However, it remains challenging to develop complete annotations of functional genes and regulatory elements in these genomes. Here, we explore the potential to use DNA methylation profiles to develop more complete and refined annotations. Using leaf tissue in maize, we define ~100,000 unmethylated regions (UMRs) that account for 5.8% of the genome; 33,375 UMRs (1.3% of the genome) are found greater than 2 kilobase pairs from genes. UMRs are highly stable in multiple vegetative tissues and they capture the vast majority of accessible chromatin regions from leaf tissue. However, many UMRs are not accessible in leaf (leaf-iUMRs) and these represent a set of genomic regions with potential to become accessible in specific cell types or developmental stages. Leaf-iUMRs often occur near genes that are expressed in other tissues and are enriched for transcription factor (TF) binding sites of TFs that are also not expressed in leaf tissue. The leaf-iUMRs exhibit unique chromatin modification patterns and are enriched for chromatin interactions with nearby genes. The total UMRs space in four additional monocots ranges from 80-120 megabases, which is remarkably similar considering the range in genome size of 271 megabases to 4.8 gigabases. In summary, based on the profile from a single tissue, DNA methylation signatures pinpoint both accessible regions and regions poised to become accessible or expressed in other tissues. Thus, UMRs can provide powerful filters to distill large genomes down to the small fraction putative functional elements and facilitate the discovery of tens of thousands of novel candidate regulatory regions.
Project description:Three different maize lines were assayed for differential gene expression in mature leaf tissue. Leaves from the Oh43 maize line are more resistant to insect larvae damage than the original parents, lines Oh40B and W8. The goal of the project was to discover genes highly expressed in the Oh43 line that potentially contributes to insect resistance. RNA was extracted from a mature leaf (third visible leaf from the top of a 7 leaf plant) of each inbred (Oh43, Oh40B, and W8). cDNA from four biological replicates of each inbred was labeled (indirect method) twice with Cy5 and twice with Cy3. A total of six microarray slides were probed with 12 different labeled cDNAs.
Project description:Eighteen genetically-diverse maize hybrids (Zea mays, dent lines crossed to a flint inbred-line) were cultivated in a growth-chamber at optimal temperature (20°C) for three weeks. They were then submitted to three successive steps of decreasing temperature ( 16, 13 and 8.5°C). Each step lasted two days. Samples were taken on the youngest ligulated leaf (fourth or fifth leaf) at the end of the period at 20°C and at the end of each temperature step. Three replicates per genotype/ temperature combination were analyzed. Each replicate was made up of the mix of leaf samples from different plants.
Project description:Epigenetic marks such as DNA methylation can act as heritable marks on a genome leading to unique regulation of genomic sequences. As a transient mark, DNA methylation has been identified as a possible mechanism for reversible genetic regulation of cells derived through either mitotic or meiotic cellular division. Although variation between epigenetic states is known to exist between individuals, there is little known about the variability of DNA methylation patterns between different developmental stages of an individual. We have assessed genome-wide DNA methylation patterns in four tissues of two inbred maize lines: B73 and Mo17. Although hundreds of regions of differential methylation are present between the two genotypes, few examples of tissue-specific DNA methylation variation were observed. The lack of clear epigenetic variation between tissues indicates the limited impact of DNA methylation on developmental processes within maize. meDIP-chip analysis of four maize tissues identifed few tissue-specific DNA methylation variable regions (tDMRs), whereas hundreds of genotype-specific DMRs were identified that were conserved across tissues. Methylation profiles for tassel, embryo, endosperm, and leaf of the maize inbred lines B73 and Mo17. Three biological replications for each tissue of each genotype were performed. A custom 2.1M NimbleGen array (GPL13499) was used for embryo, endosperm, and leaf, and a custom 3x1.4M NimbleGen array containing a subset of probes from the 2.1M NimbleGen array (GPL15621) was used for tassel. All of the processed data is based on the largest number of comparable probes (~1.4M) between the two arrays.
Project description:The maize inbred line A661 shows a characteristic phenotype when grown at suboptimal temperatures for three weeks and then is exposed to optimal temperatures for one extra week. After this period the third leaf showed two well defined sections: distal (chlorophyll-less; CL) and proximal (chlorophyll-containing; CC) sections. To further investigate the performance of the inbred line A661 under cold conditions a gene expression profiling analysis was conducted using large scale maize microarrays. A total of 1002 transcripts change their expression between both leaf sections and the majority of these codify for proteins located to the chloroplast.
Project description:Modern maize was domesticated from Teosinte parviglumis, with subsequent introgressions from Teosinte mexicana, yielding increased kernel row number, loss of the hard fruit case and dissociation from the cob upon maturity, as well as fewer tillers. Molecular approaches have identified several transcription factors involved in the development of these traits, yet revealed that a complex regulatory network is at play. MaizeCODE deploys ENCODE strategies to catalog regulatory regions in the maize genome, generating histone modification and transcription factor ChIP-seq in parallel with transcriptomics datasets in 5 tissues of 3 inbred lines which span the phenotypic diversity of maize, as well as the teosinte inbred TIL11. Integrated analysis of these datasets resulted in the identification of a comprehensive set of regulatory regions in each inbred, and notably of distal enhancers which were differentiated from gene bodies by their lack of H3K4me1. Many of these distal enhancers expressed noncoding enhancer RNAs bi-directionally, reminiscent of “super enhancers” in animal genomes. We show that pollen grains are the most differentiated tissue at the transcriptomic level, and share features with endosperm that may be related to McClintock’s chromosome breakagefusion-bridge cycle. Conversely, ears have the least conservation between maize and teosinte, both in gene expression and within regulatory regions, reflecting conspicuous morphological differences selected during domestication. The identification of molecular signatures of domestication in transcriptional regulatory regions provides a framework for directed breeding strategies in maize.
Project description:Using the RL-SAGE method (Gowda et al. 2004), a maize leaf longSAGE library (cv. inbred line B73) was constructed. Leaf tissues were harvested from 4-week old B73 plants for RNA isolation. The conditions in the growth chamber were 12 h light (500 µmol photons m-2 sec-1), 20oC at night, 26oC in the day and 85% relative humidity. A total of 44,870 unique tags (17 bases +CATG) were identified from 232,948 individual tags in the maize leaf library.
Project description:Eighteen genetically-diverse maize hybrids (Zea mays, dent lines crossed to a flint inbred-line) were cultivated in the field. Two conditions of cultivation were analyzed: normal sowing and early sowing. Upon early sowing plants grew under lower temperatures than upon normal sowing. Young leaves were harvested for proteomics quantitative analysis after a thermal time (equivalent number of days after emergence at 20°C) of 17 to 18. Three replicates per genotype/condition combination were analyzed. Each replicate was made up of the mix of leaf samples of five different plants.