Dataset Information

Gene expression analyses in maize inbreds and hybrids with varying levels of heterosis.

ABSTRACT: BACKGROUND: Heterosis is the superior performance of F1 hybrid progeny relative to the parental phenotypes. Maize exhibits heterosis for a wide range of traits, however the magnitude of heterosis is highly variable depending on the choice of parents and the trait(s) measured. We have used expression profiling to determine whether the level, or types, of non-additive gene expression vary in maize hybrids with different levels of genetic diversity or heterosis. RESULTS: We observed that the distributions of better parent heterosis among a series of 25 maize hybrids generally do not exhibit significant correlations between different traits. Expression profiling analyses for six of these hybrids, chosen to represent diversity in genotypes and heterosis responses, revealed a correlation between genetic diversity and transcriptional variation. The majority of differentially expressed genes in each of the six different hybrids exhibited additive expression patterns, and approximately 25% exhibited statistically significant non-additive expression profiles. Among the non-additive profiles, approximately 80% exhibited hybrid expression levels between the parental levels, approximately 20% exhibited hybrid expression levels at the parental levels and ~1% exhibited hybrid levels outside the parental range. CONCLUSION: We have found that maize inbred genetic diversity is correlated with transcriptional variation. However, sampling of seedling tissues indicated that the frequencies of additive and non-additive expression patterns are very similar across a range of hybrid lines. These findings suggest that heterosis is probably not a consequence of higher levels of additive or non-additive expression, but may be related to transcriptional variation between parents. The lack of correlation between better parent heterosis levels for different traits suggests that transcriptional diversity at specific sets of genes may influence heterosis for different traits.

SUBMITTER: Stupar RM

PROVIDER: S-EPMC2365949 | biostudies-literature | 2008

REPOSITORIES: biostudies-literature

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Gene expression analyses in maize inbreds and hybrids with varying levels of heterosis.

Stupar Robert M RM Gardiner Jack M JM Oldre Aaron G AG Haun William J WJ Chandler Vicki L VL Springer Nathan M NM

BMC plant biology 20080410

<h4>Background</h4>Heterosis is the superior performance of F1 hybrid progeny relative to the parental phenotypes. Maize exhibits heterosis for a wide range of traits, however the magnitude of heterosis is highly variable depending on the choice of parents and the trait(s) measured. We have used expression profiling to determine whether the level, or types, of non-additive gene expression vary in maize hybrids with different levels of genetic diversity or heterosis.<h4>Results</h4>We observed th ...[more]

PMID: 18402703

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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.

Dataset Information

Gene expression analyses in maize inbreds and hybrids with varying levels of heterosis.

Publications

Gene expression analyses in maize inbreds and hybrids with varying levels of heterosis.

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