Heritable epigenetic variation among maize inbreds
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ABSTRACT:
ORGANISM(S): Zea mays
SUBMITTER: Ruth Swanson-Wagner
PROVIDER: E-GEOD-29099 | biostudies-arrayexpress |
REPOSITORIES: biostudies-arrayexpress
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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.
2012-08-27 | E-GEOD-38503 | biostudies-arrayexpress
Project description:DNA methylation is a chromatin modification that is frequently associated with epigenetic regulation in plants and mammals. However, other genetic changes such as transposon insertions also can lead to changes in DNA methylation levels. Genome-wide profiles of DNA methylation levels for 20 maize inbreds were used to discover differentially methylated regions (DMRs). The methylation level for each of these DMRs was also assayed in 31 additional maize genotypes resulting in the discovery of 1,966 common DMRs and 1,754 rare DMRs. Analysis of recombinant inbred lines provides evidence that the majority of DMRs are heritable. A local association scan found that nearly half of the DMRs with common variation are significantly associated with SNPs found within or near the DMR. Many of the DMRs that are significantly associated with local genetic variation are found near transposable elements that may contribute to the DNA methylation variation. The analysis of gene expression in the same samples used for DNA methylation profiling identifies over 300 genes with expression patterns that are significantly associated with the DNA methylation variation among genotypes. Collectively, our results suggest that DNA methylation variation is influenced by genetic and epigenetic variation is often stably inherited and can influence expression level of genes in the population. Methylation profiles in seedling tissue of a panel of 51 maize inbred lines using a custom 2.1M or 1.4M feature NimbleGen array. Methylation profiles in seedling tissue of maize inbred lines, teosinte and recombinant inbred lines (RILs) derived from B73 and Mo17 using a custom 12x270K NimbleGen array. Inbred lines B73 and Mo17 each had 3 biological replicates, the other sample had 1 replicate.
2013-08-12 | E-GEOD-46949 | biostudies-arrayexpress
Project description:Imprinting describes the differential expression of alleles based upon their parent of origin. Deep sequencing of RNAs from maize endosperm and embryo tissue 14 days after pollination was used to identify imprinted genes among a set of ~12,000 genes that were expressed and contained sequence polymorphisms between the B73 and Mo17 genotypes. The analysis of parent-of-origin patterns of expression resulted in the identification of 100 putative imprinted genes in maize endosperm including 54 maternally expressed genes (MEGs) and 46 paternally expressed genes (PEGs). Three of these genes have been previously identified as imprinted while the remaining 97 genes represent novel imprinted maize genes. A genome-wide analysis of DNA methylation identified regions with reduced endosperm DNA methylation in, or near, 19 of the 100 imprinted genes. The reduced levels of DNA methylation in endosperm are caused by hypomethylation of the maternal allele for both MEGs and PEGs in all cases tested. Many of the imprinted genes with reduced DNA methylation levels also show endosperm-specific expression patterns. The imprinted maize genes were compared with imprinted genes identified in genome-wide screens of rice and Arabidopsis and at least 10 examples of conserved imprinting between maize and each of the other species were identified. Methylation profiles across endosperm tissue in B73 and Mo17 were assayed for three biological replications using a custom 2.1M gene-focused NimbleGen array.
2011-12-16 | E-GEOD-33730 | biostudies-arrayexpress
Project description:DNA methylation is a chromatin modification that contributes to epigenetic regulation of gene expression. The inheritance patterns and trans-generational stability of 962 differentially methylated regions (DMRs) were assessed in a panel of 71 near-isogenic lines (NILs) derived from maize (Zea mays) inbred lines B73 and Mo17. The majority of DMRs exhibit inheritance patterns that would be expected for local (cis) inheritance of DNA methylation variation such that DNA methylation level was coupled to local genotype. There are few examples of DNA methylation that exhibit trans-acting control or paramutation-like patterns. The cis-controlled DMRs provided an opportunity to study the stability of inheritance for DNA methylation variation. There was very little evidence for alterations of DNA methylation levels at the cis-controlled DMRs during NIL population development. DNA methylation level was associated with local genotypes in all of the >30,000 examined cases except one. Additionally, the majority of the DMRs were not associated with small RNA. Together, our results suggest that a significant portion of DNA methylation variation in maize exhibits cis-controlled inheritance patterns, is highly stable and does not require active programming by small RNAs for maintenance. Methylation profiles in seedling tissue of maize near-isogenic lines (NILs) derived from B73 and Mo17 using a custom 12x270K NimbleGen array.
2014-04-01 | E-GEOD-51567 | biostudies-arrayexpress
Project description:Transposable elements have the potential to act as controlling elements to influence the expression of genes. The current paradigm suggests that heterochromatic silencing can spread beyond the borders of the transposable element and influence the chromatin state of neighboring low-copy sequences. This would allow transposable elements to condition obligatory or facilitated epialleles and act as controlling elements. The maize genome contains numerous families of class I transposable elements (retrotransposons) that are present in moderate to high copy numbers and many are found in regions near genes which provides an opportunity to test whether the spreading of heterochromatin from retrotransposons is prevalent. We have investigated the extent of heterochromatin spreading into flanking DNA around each family of retrotransposons through profiling of DNA methylation and di-methylation of lysine 9 of histone 3 (H3K9me2) in low-copy regions of the maize genome. The effects of different retrotransposon families on local chromatin are highly variable. Some LTR families exhibit enrichment of heterochromatic marks within 800-1200 base pairs of the insertion site while other families have very little evidence for spreading of heterochromatic marks. The analysis of chromatin state in genotypes that lack specific insertions suggests that the adjacent heterochromatin results from spreading of silencing rather than insertion-site preferences. Genes that are located near elements that exhibit spreading of heterochromatin tend to be expressed at lower levels than other genes. Our findings suggest that a subset of LTR retrotransposon families may act as controlling elements influencing neighboring sequences while the majority of elements have little effect on flanking sequences Transposable elements comprise a substantial portion of many eukaryotic genomes. These mobile fragments of DNA can result in mutations through insertions into genes but may also affect the regulation of genes they insert near. There is evidence that the majority of transposable elements are epigenetically silenced and in some cases this silencing may affect neighboring sequences. However, evolutionary theory would predict that there would be selective pressures for transposable elements to limit their effects on neighboring genes. The maize genome has a complex organization with many genes flanked by retrotransposons. We profiled the spread of heterochromatin from the retrotransposons into nearby low copy sequences for 150 high copy retrotransposon families. While the manymajority of retrotransposons exhibit little to no spreading of heterochromatin there are a small number ofsome retrotransposon families that influence the chromatin state of surrounding regions. The families may represent bad “neighbors” that spread heterochromatin and influence nearby genes. 6 total samples: 3 replicates of B73 H3k9 and 3 replicates of Mo17 H3k9 3 total samples: mop1 mutant, b73.zmet2 (zmet2.m1 mutant in B73 background) and mo17.zmet2 (zmet2.m1 mutant in Mo17 background)
2012-11-26 | E-GEOD-39460 | biostudies-arrayexpress
Project description:The complexity of the maize (Zea mays) genome makes it an ideal system for the study of both genetics and epigenetics. Here, we generated the integrated maps of transcriptomes and epigenomes of shoots and roots of two maize inbred lines and their reciprocal hybrids, and globally surveyed the epigenetic variations and their relationships with transcriptional divergence between different tissues and different genotypes. We observed that whereas histone modifications vary both between tissues and between genotypes, DNA methylation patterns are more distinguishable between genotypes than between tissues. Histone modifications were associated with transcriptomic divergence between tissues and between hybrids and parents. Further, we show that genes up-regulated in both shoots and roots of hybrids were significantly enriched in the nucleosome assembly pathway. Interestingly, 22- and 24-nt siRNAs were shown to be derived from distinct transposable elements (TEs), and for different TEs in both shoots and roots, the differences in siRNA activity between hybrids and patents were primarily driven by different siRNA species. Together, our results suggest that despite of the variations in specific genes or genomic loci, similar mechanisms may account for the genome-wide epigenetic regulation of gene activity and transposon stability in different tissues of maize hybrids. Genome-wide integrated maps of mRNA and small RNA (sRNA) transcriptomes, DNA methylomes and genome-wide distribution of three representative histone modifications (H3K4me3, H3K9ac and H3K36me3) in the shoots and roots of 14 day old seedlings of two maize inbred lines (B73 and Mo17) and their reciprocal hybrids (B73 x Mo17 and Mo17 x B73).
2013-03-19 | E-GEOD-43142 | biostudies-arrayexpress
Project description:Small RNAs (sRNAs) are hypothesized to contribute to hybrid vigor because they maintain genome integrity, contribute to genetic diversity, and control gene expression. We used Illumina sequencing to assess how sRNA populations vary between two maize inbred lines (B73, Mo17) and their hybrid. We sampled sRNAs from the seedling shoot apex and the developing ear, two rapidly growing tissues that program the greater growth of maize hybrids. We found that parental differences in siRNAs primarily originate from repeat regions. Although the maize genome contains greater number and complexity of repeats compared to Arabidopsis or rice, we confirmed that like these simpler plant genomes, 24-nt siRNAs whose abundance differs between maize parents also show a trend of downregulation following hybridization. Surprisingly, hybrid vigor is fully maintained when 24-nt siRNAs are globally reduced by mutation of the RNA-dependent RNA polymerase2 (RDR2) encoded by modifier of paramutation1 (mop1). We also discovered that 21-22nt siRNAs derived from a number of distinct retrotransposon families differentially accumulate between B73 and Mo17 as well as their hybrid. Thus, maize possesses a novel source of genetic variation for regulating both transposons and genes at a genomic scale, which may contribute to its high degree of observed heterosis. sRNA libraries were derived from RNA isolated from the seedling shoot apex and developing ear tissues from B73, Mo17, B73xMo17 and Mo17xB73. The shoot apex was chosen because it is enriched for meristematic tissue where cell proliferation occurs, rates of organ initiation are determined, and organ size is specified. The developing ear was examined because it is enriched in meristematic tissue and is undergoing rapid growth, and also because the mature ear shows the highest degree of heterosis. Total RNA was isolated and separated on a 15% TBE-Urea polyacrylamide gel. Using a 10-bp ladder, the sRNA fraction representing 10-40-bp was excised. sRNA libraries were prepared according to Lu et al. (2007) or manufacturer's instructitions (Illumina). A combination of Perl scripts and FASTX toolkit scripts were used to remove adapters, collapse identical sequences and count reads per sequence. Supplementary processed data text files contain the distinct sRNA sequences for all of the genotypes analyzed in that experiment. Abundance (reads per million) was calculated for each distinct sequence by dividing the number of reads of distinct sRNA in a library by the total number of sRNA reads for that library and multiplying this by 1 million. Genome builds: B73 genome, maizesequence.org release 4a.53 (October, 2009); Mo17 whole genome shotgun clones.
2012-05-26 | E-GEOD-37411 | biostudies-arrayexpress
Project description:Following the domestication of maize over the past ,10,000 years, breeders have exploited the extensive genetic diversity of this species to mold its phenotype to meet human needs. The extent of structural variation, including copy number variation (CNV) and presence/absence variation (PAV), which are thought to contribute to the extraordinary phenotypic diversity and plasticity of this important crop, have not been elucidated. Whole-genome, array-based, comparative genomic hybridization (CGH) revealed a level of structural diversity between the inbred lines B73 and Mo17 that is unprecedented among higher eukaryotes. A detailed analysis of altered segments of DNA conservatively estimates that there are several hundred CNV sequences among the two genotypes, as well as several thousand PAV sequences that are present in B73 but not Mo17. Haplotype-specific PAVs contain hundreds of single-copy, expressed genes that may contribute to heterosis and to the extraordinary phenotypic diversity of this important crop. In our experimental design we had seven replicates of B73 (one with Cy3 and six with Cy5) and seven replicates of Mo17 (six with Cy3 and one with Cy5). Images were processed and spatial normalization of data within the array was conducted according to Nimblegen's standard protocol. The RIL samples (M0022 and M0023) were in included because we used the probe's B73 and Mo17 signals of those samples during our analysis.
2009-11-19 | E-GEOD-16938 | biostudies-arrayexpress
Project description:DNA methylation is a chromatin modification that is sometimes associated with epigenetic regulation of gene expression. As DNA methylation can be reversible at some loci, it is possible that methylation patterns may change within an organism that is subjected to environmental stress. In order to assess the effects of abiotic stress on DNA methylation patterns in maize (Zea mays), we subjected seedlings to heat, cold and UV stress treatments. Tissue was later collected from individual adult plants that had been subjected to stress or control treatments and used to perform DNA methylation profiling to determine whether there were consistent changes in DNA methylation triggered by specific stress treatments. The DNA methylation profiling was performed by immunoprecipitation of methylated DNA followed by microarray hybridization to allow for quantitative estimates of DNA methylation abundance throughout the low-copy portion of the maize genome. By comparing the DNA methylation profiles of each individual plant to the average of the control plants it was possible to identify regions of the genome with variable DNA methylation. However, we did not find evidence of consistent DNA methylation changes resulting from the stress treatments used in this study. Instead, the data suggest that there is a low-rate of stochastic variation that is present in both control and stressed plants. Methylation profiles in flag leaf tissue of maize inbred lines under various stress conditions using a custom 1.4M feature NimbleGen array. Methylation profiles of flag leaf tissue from 18 B73 inbred lines that underwent various stresses as seedlings. This includes 5 cold treatment plants, 4 UV treated plants, 3 heat treated plants, and 6 total control plants (no stress). All methylation profiling was done on a custon 3x1.4M NimbleGen array platform (meDIP-chip).
2016-01-07 | E-GEOD-65266 | biostudies-arrayexpress
Project description:we determine genome-wide binding profiles of a maize CCA1 homolog, ZmCCA1b, in maize inbreds and F1 hybrids at different times of the day. ZmCCA1b is characterized as a central clock regulator gene with evolutionarily conserved molecular and circadian functions and nonadditively expressed in F1 hybrid seedlings. ZmCCA1b binds to over 4,300 target genes in the maize genomes, of which annotation confirms energy metabolic pathways as the main output. We report that an altered temporal binding activity of ZmCCA1b in the hybrid seedlings, which increases expression of carbon fixation genes, increases carbon fixation rates and biomass, demonstrating a novel example of how circadian-regulatory networks directly contribute to growth vigor in maize hybrids. These results collectively offer new insights into clock-mediated regulation of growth vigor in hybrid plants and crops. Profiling genome-wide binding events of ZmCCA1b in the maize inbreds and F1 hybrids at ZT3, ZT9 and ZT15 using chromatin immunoprecipitation followed by deep sequencing (ChIP-seq). 2 biological replicates for each sample were used. Input DNA sample corresponding to each ChIP sample was also sequenced in parallel. We have developed a native antibody for the protein (GRMZM2G014902; epitope: residues 11-77) for the ChIP-seq study.
2016-06-30 | E-GEOD-67655 | biostudies-arrayexpress