Unknown,Transcriptomics,Genomics,Proteomics

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Regulation of Gene Expression and Parent-of-Origin Effects in Maize Hybrids

ABSTRACT: Heterosis (hybrid vigor) refers to the superior performance of hybrid progeny relative to their parents. Although widely exploited in agriculture, the mechanisms responsible for heterosis are not well understood. As a monoecious organism, a given maize plant can be used as both male and female parents of crosses. Regardless of the cross direction, the maize inbred lines B73 and Mo17 produce hybrids that substantially out-perform their parents. These reciprocal hybrids differ phenotypically from each other despite having identical nuclear genomes. Consistent with these phenotypic observations, 30-50% of genes were differentially expressed between these reciprocal hybrids. An eQTL experiment conducted to better understand the regulation of gene expression in inbred and hybrid lines detected ~4,000 eQTL associations. The majority of these eQTL act in trans to regulate expression of genes on other chromosomes. Surprisingly, many of the trans-eQTL, when heterozygous, differentially regulated transcript accumulation in a manner consistent with gene expression in the hybrid being regulated exclusively by the paternally transmitted allele. The design of the eQTL experiment controlled for cytoplasmic and maternal effects, suggesting that widespread paternal genomic imprinting contributes to the regulation of gene expression in maize hybrids. Keywords: eQTL, parent-of-origin GPL4521 - SAM1.2 (Reciprocal Hybrid Comparison): Six replications of B73xMo17 and Mo17xB73 were grown in growth chambers to tightly control environmental variation. Seeds from each genotype were taken from a single source (ear) for all six replications. Within each replication, genotypes were randomly assigned growth locations. Six healthy seedlings for each genotype and replication were harvested at two weeks of age. For each replication, B73xMo17 and Mo17xB73 were hybridized to the SAM1.2 microarray (GPL4521) using a randomized, alternate dye assignment. GPL3333 - SAM1.1 and GPL3538 - SAM3.0 (eQTL Experiment): Four biological replications of the RIL, B73xRIL, and Mo17xRIL cross-types were planted in growth chambers using seed from a single source for each genotype. Each RIL and its crosses onto B73 and Mo17 were planted using a split-plot design with RIL group (RIL and its cross onto B73 and Mo17) as the whole-plot treatment factor and cross-type (RIL, B73xRIL, and Mo17xRIL) as the split-plot treatment factor. The whole-plot portion of the experiment was designed as a randomized complete block design with four replications carried out on four separate occasions in the same environment. For the split-plot portion of the design, twelve seedlings of each RIL and its crosses were randomized within two adjacent flats in a growth chamber (six healthy seedlings per genotype were randomly chosen and pooled at harvest). For each replication, RIL, B73xRIL, and Mo17xRIL cross-types were hybridized to custom cDNA microarrays using a loop design such that each loop included all pairwise comparisons between the RIL and its crosses with B73 and Mo17. Four biological replications were hybridized to the SAM1.1 (GPL3333) array and two of the four biological replications were hybridized to SAM3.0 (GPL3538). RNA samples were alternately labeled to provide dye balance within each loop and replication. GPL8734 - Gene Expression between two maize reciprocal hybrids Heterosis refers to the enhanced agronomic performance of a hybrid relative to its (usually) inbred parents. We have previously documented widespread differences in gene expression in the B73xMo17 hybrid relative to its inbred parents B73 and Mo17 (Swanson, et al., 2006, PNAS). The reciprocal B73xMo17 and Mo17xB73 hybrids are both highly heterotic, but despite having identical nuclear genomes exhibit statistically significant differences in multiple traits. RNA-seq experiment was conducted to compare the gene expression globally between the two reciprocal hybrids. 1 samples from B73XMo17 and Mo17XB73 RNAs were extracted from a single replication of 14-day-old B73xMo17 and Mo17xB73 seedlings. RNAs were purified using DNaseI treatment followed by cleanup with the RNeasy Plant Mini Kit (Qiagen, Valencia, CA) as per manufacturer instructions. Sequencing library construction was completed using the Illumina mRNA-Seq sample preparation kit. Processed data file 'ZmB73_4a.53_filtered_genes.fasta' and its README file are linked below as supplementary files. The fasta file contains the gene model ID and corresponding sequence generated from maize genome project. This fasta file was used for the following samples: GSM418173, GSM418174, GSM420173, GSM420174, GSM422828, GSM422829.

ORGANISM(S): Zea mays

SUBMITTER: Patrick Schnable

PROVIDER: E-GEOD-16136 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Publications

Paternal dominance of trans-eQTL influences gene expression patterns in maize hybrids.

Swanson-Wagner Ruth A RA DeCook Rhonda R Jia Yi Y Bancroft Tim T Ji Tieming T Zhao Xuefeng X Nettleton Dan D Schnable Patrick S PS

Science (New York, N.Y.) 20091101 5956

Heterosis refers to the superior performance of hybrid progeny relative to their inbred parents, but the mechanisms responsible are unknown. Hybrids between the maize inbred lines B73 and Mo17 exhibit heterosis regardless of cross direction. These reciprocal hybrids differ from each other phenotypically, and 30 to 50% of their genes are differentially expressed. We identified approximately 4000 expression quantitative trait loci (eQTL) that allowed us to identify markers linked to variation in e ...[more]

PMID: 19965432

Publication: 1/2

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Project description:Heterosis is the phenomenon whereby the progeny of particular inbred lines have enhanced agronomic performance relative to both parents. Although several hypotheses have been proposed to explain this fundamental biological phenomenon, the responsible molecular mechanisms have not been determined. The maize inbred lines B73 and Mo17 produce a heterotic F1 hybrid. Global patterns of gene expression were compared in seedlings of these three genotypes using a microarray that contains 13,999 cDNAs. Using an estimated 15% false discovery rate as a cut-off, 1,367 ESTs (9.8%) were identified as being significantly differentially expressed among genotypes. All possible modes of gene action were observed, including additivity, high- and low-parent dominance, under-dominance, and over-dominance. The largest proportion of the ESTs (78%, 1,062/1,367) exhibited expression patterns that are not statistically distinguishable from additivity. Even so, 22% of the differentially regulated genes exhibited non-additive modes of gene expression. Classified on the basis of significant pair-wise comparisons of genotype means, 181 of these 305 genes exhibited high-parent dominance and 23 exhibited low-parent dominance. In addition, 44 genes exhibited under- or over-dominant gene action. These findings are consistent with the hypothesis that multiple molecular mechanisms contribute to heterosis, including over-dominance Keywords: Genotype Comparison The inbreds B73 (Schnable Lab Accession #660) and Mo17 (Schnable Lab Accession #2618) used in this study were derived by self-pollination from stocks originally obtained from Don Robertson (Iowa State University) and Mike Lee (Iowa State University), respectively. Mo17 was crossed as a female by B73 to generate the F1. Kernels from three different seed sources (ears) per genotype were used in the experimental design. Prior to microarray analyses genotypes were confirmed by genotyping DNA extracted from each seed source using co-dominant IDP genetic markers that distinguish B73 from Mo17 (Fu et al., in preparation). Ten biological replications of B73, Mo17, and their F1 (Mo17xB73) were grown under highly controlled conditions in a randomized complete block design. For each replication, the B73, Mo17, and F1 samples were hybridized to three two-color cDNA microarrays using a loop design such that each loop included all pairwise comparisons between genotypes. RNA pools for each genotype were alternately labeled providing dye balance within each loop. After hybridization, one biological replicate was removed due to poor quality. The final analysis incorporated 27 microarray slides (3 slides for each of nine high-quality biological replicates).

Project description:Natural Antisense Transcripts (NATs) can regulate gene expression by virtue of their ability to form double-stranded RNA duplexes. To investigate NATs in the maize transcriptome, cDNAs from seedling of two inbred lines (B73 and Mo17) were hybridized to an oligonucleotide microarray designed to validate the expression of in silico detected NATs and to screen for NATs that can anneal to a random set of 3â UTRs and selected repeats found in 3â UTRs regions. Quantitative Real-Time PCR experiments were conducted to determine the minimum detection threshold of microarray experiment and to thereby identify genes for which both sense and antisense transcripts accumulate to detectable levels. Two independent approaches, strand-specific RT-PCR and S1 nuclease assays were conducted to validate the results of the microarray experiment. Based on these conservative assays, NATs accumulate in seedlings that can anneal to over 70% of a random set of maize genes. In addition, both sense and antisense transcripts anneal to more than 80% of a set of maize repeats. Significantly, sense and antisense transcripts exhibit significant different expression patterns between the two genotypes. Based on these findings we hypothesize that interactions between sense and antisense transcripts may contribute to the differential patterns of gene expression in maize hybrids and to heterosis. Keywords: Global antisense transcripts profiling between two maize inbreds To systematically identify NATs in maize, we employed multiple strategies to computationally identify putative antisense transcripts from our partial genome assembly (MAGIs) and a collection of ESTs we sequenced with known sequence orientation. Additionally, we randomly sampled and surveyed maize UTRs which often harbor transposons. Strand-specific oligonucleotides which can hybridize to the antisense strand were designed and spotted with together with the oligonucleotides hybridizing sense strands on a custom, strand-specific oligoarray, providing the first global expression profiling study of NATs in maize UTRs. In total, 10 biological replication were conducted to compare the global gene expression profiles between two maize genotypes (B73 and Mo17).

Project description:Vegetative phase change is the developmental transition from the juvenile phase to the adult phase during which a plant becomes competent for sexual reproduction. Gain of ability to flower is often accompanied by changes in patterns of differentiation in newly forming vegetative organs. In maize, juvenile leaves differ from adult leaves in morphology, anatomy, and cell wall composition. Whereas the normal sequence of juvenile followed by adult is repeated with every sexual generation, this sequence can be altered in maize by the isolation and culture of the shoot apex from an adult phase plant; an âadultâ meristem so treated reverts to forming juvenile vegetative organs. To investigate the molecular differences between the juvenile and adult phases in maize comparisons among two juvenile samples, leaf 4 and culture-derived leaf 3 or 4, and an adult sample (leaf 9) were made using cDNA microarrays. All samples were leaf primordia at plastochron 6. A gene was scored as âphase specificâ if it was up- (or down-) regulated in both juvenile samples compared to the adult sample with at least a twofold-change in gene expression at P-value less than or equal to 0.005. Some 221 ESTs up-regulated in juvenile and 28 ESTs up-regulated in adult were identified. Altered patterns of expression of selected ESTs in the phase change mutants Tp2, d1 and gl15 further confirmed these genes as being phase-specific and allowed us to position these genes in the known genetic hierarchy regulating phase change. Keywords: Transcript profiling among seed-derived juvenile leaf 4 and adult leaf 9 and culture-rejuvenated leaf 3 or 4 in maize To identify juvenile or adult specific ESTs, total RNA from leaf primordia at plastochron 6 (P6) was isolated from leaves 4 (L4) and 9 (L9) from seed-derived plants and leaf 3 or 4 (RL3/4) from culture-derived plants. For each of six biological replications, each of the three pairwise comparisons of P6-staged leaf primordia from L4, L9 and RL3/4 was made on one slide. With six biological replications and three slides per replication (L4 vs. L9, L9 vs. RL3/4, RL3/4 vs. L4), this replicated loop design used a total of 18 slides. To ensure dye balance, each of the 18 target samples was measured once with Cy3 labeling and once with Cy5 labeling.

Project description:All above ground organs of higher plants are ultimately derived from specialized organogenic structures termed shoot apical meristems (SAMs). The SAM exhibits distinctive structural organization, marked by cell layering. Maize SAMs are comprised of two cell layers, L1 (single cell layered tunica) and L2 (corpus). To identify genes required for layer-specific functions intact maize SAMs were fixed, embedded in paraffin and sectioned. L1 and L2 cells were isolated from these sections via laser capture microdissection (LCM). RNA was isolated from six biological replications of L1 and L2, amplified and hybridized to microarrays spotted with ~37,000 maize cDNA clones. This experiment identified ~700 ESTs that are preferentially expressed in the L1 or the L2 (P <0.001). The L1-up-regulated ESTs included ZmOCL1 and ZmOCL4, which are known to exhibit L1-specific expression in the maize SAM. The L2-up-regulated ESTs included KNOTTED1, whose transcripts are known to accumulate in the L2 but not in the L1 of the maize SAM. Differentially expressed ESTs included genes involved in transcription, signal transduction, transport and metabolism, many of which are novel candidates that are required for layer-specific functions in the maize SAM. Several L1-up-regulated ESTs were annotated as yabby family genes or basic helix-loop-helix transcription factor-like genes, which have not previously been reported as having layer-specific expression in the SAM. Novel WW domain-containing genes (WW genes) were identified in this study. The WW domain mediates protein-protein interactions, often with signal transduction components. These WW genes were substantially up-regulated in the L1 relative to the L2. Keywords: Cell Type Comparison An experimental aim is to identify genes that are differentially expressed in distinct histological cell layers of maize SAM by comparing the transcript accumulation between L1 (single cell layered tunica) and L2 (corpus) using cDNA microarrays that have over 37,000 informative spots from maize.

Project description:Although studies have established that exogenous growth hormone (GH) treatment stimulates growth in fish, its effects on target tissue gene expression are not well characterized. We assessed the effects PosilacÂ® (Monsanto Co., St. Louis, MO), a recombinant bovine somatotropin, on tissue transcript levels. Transcript abundance was measure in liver and muscle using the GRASP 16 K cDNA microarray. A selection of the genes identified as altered with the microarray, and also transcripts for insulin-like growth factors, growth hormone receptors (GHR) and myostatins were measured by realtime PCR in the liver, muscle, brain, kidney, intestine, stomach, gill and heart. In general, transcripts identified as differentially regulated in the muscle on the microarray showed similar direction of expression in the other non-hepatic tissues. Rainbow trout were selected from two high growth rate and two low growth rate families. A total of 113 and 67 transcripts were identified by microarray as differentially expressed with GH treatment across growth rate for muscle and liver respectively. The largest proportion of the transcripts represented novel transcripts, followed by immune and metabolism related genes. The immune related genes were primarily modulated in the liver and indicate activation of a non-specific immune response. The metabolic genes include lipid metabolism, oxidative phosphorylation and one carbon metabolism pathway transcripts. Most notable among the growth axis genes measured by realtime PCR were increases in GHR1 and-2 transcript in liver and muscle. Our results indicate that short-term GH treatment activates the immune system, shifts the metabolic sectors and modulates growth regulating genes. Keywords: Growth Hormone Injection Muscle and Liver Gene Expression Rainbow trout (hatched March 2005) selected for extreme growth rate were obtained from NCCCWA brood stock. Families were selected based on body weight at 7 months of age and thermal growth coefficient for the final month of growth. The two high growth families used in the study were in the top 2% in terms of growth rate, and the low growth families were in the lowest 10% for growth rate. Fish acclimated to the new tanks for two weeks prior to initiation of the treatments. Fish from each family were randomly selected to receive one of three treatments: 1) PosilacÂ® injection (120 mg/kg BW, n = 4 per family); 2) vehicle injection (n = 4 per family); or 3) untouched controls (n = 2 per family). We had determined there was no effect to growth or the GH/IGF-I axis in the vehicle treated fish, and therefore, all of the microarray hybridizations were made between the GH and vehicle injected groups. This study included a total of 16 two-channel arrays designed for the direct comparison of GH treatment levels. That is, for each of the four groups, 1) High Growth Rate Liver; 2) Low Growth Rate Liver; 3) High Growth Rate Muscle; and 4) Low Growth Rate Muscle, four slide were hybridizes using individual RNA samples from individual fish. RNA isolation from each tissue/organ sample was handled separately (without pooling) with the purpose of using biological replications. We hybridized two slides with the GH cDNA labeled with Alexa 555 and vehicle cDNA labeled with Alexa 647; and two slides, using unique RNA samples, for the with GH cDNA labeled with Alexa 647 and tissue from the vehicle injected group labeled with Alexa 647 within each tissue and growth rate. Sixteen slides were used in the current study representing 32 individual tissue samples, meaning a total of four biological replicates for each treatment group.

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Project description:The transcriptional response of Atlantic salmon (Salmo salar) to infectious hematopoietic necrosis (IHN) virus was elucidated using 16,008 gene GRASP cDNA microarrays. S. salar were exposed to the IHN virus in a waterborne challenge, and kidney samples from five fish sampled on each of days 0, 1, 5 and 9 were analysed in the microarray study. Validation of nine of the significant genes was conducted on fish sampled on alternate days from 1 to 13 and compared to the unchallenged control sampled on day 0. The key pathways up-regulated in response to the virus included endosomal transport, type I and II interferon responses, the alternative complement pathway, apoptosis, phagocytosis and phagocytic cell oxidation, natural killer cell activity, antiviral replication via iron sequestering, virally-induced disruption of the cell cycle, retroviral DNA integration, T-cell activation and cellular immunity. Fish that did not contain viral titer on days 5 and 9 responded in a similar manner to those with titer, but further induced a number of genes involved in anti-viral replication (Glutathione peroxidase 1 and ferritin H), anti-proliferation (PTEN and B-cell receptor associated protein 32), lysosomal response (CD63 antigen), pro-inflammatory response (lipopolysaccharide binding protein, stress activated JNK1, thiol peroxidase), and T-cell activation (T-cell activation Rho-GTPase activating protein) that may increase resistance to the virus. Three genes that were potentially co-opted by the virus to enhance infectivity were also identified, including uPAR (angiogenesis), CypA (viral replication and infectivity), and BAF1 (viral protein biosynthesis). Perhaps the most notable finding was the up-regulation of uPAR which can function to increase the density of fibronectin, the receptor of the IHN virus, on the cell surface, hence facilitate viral entry into the cell. Keywords: Immunlogical response to IHN virus challenge A preliminary microarray experiment was run on the waterborne-challenged S. salar whereby the five individuals sampled on a given day were combined and run on a single slide, and we compared the expression profiles from each day (days 0 (unchallenged control) through 11). From this experiment, we noted that the most profound changes were occurring around days 1, 5, and 9, so we performed subsequent experiments at these time points, with five fish per day and 5 control fish analysed in total.

Dataset Information

Regulation of Gene Expression and Parent-of-Origin Effects in Maize Hybrids

Publications

Paternal dominance of trans-eQTL influences gene expression patterns in maize hybrids.

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