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Gene loss, silencing and activation in a newly synthesized wheat allotetraploid.

ABSTRACT: We analyzed the events that affect gene structure and expression in the early stages of allopolyploidy in wheat. The transcriptome response was studied by analyzing 3072 transcripts in the first generation of a synthetic allotetraploid (genome S(l)S(l)A(m)A(m)), which resembles tetraploid wheat (genome BBAA), and in its two diploid progenitors Aegilops sharonensis (S(l)S(l)) and Triticum monococcum ssp. aegilopoides (A(m)A(m)). The expression of 60 out of 3072 transcripts was reproducibly altered in the allotetraploid: 48 transcripts disappeared and 12 were activated. Transcript disappearance was caused by gene silencing or by gene loss. Gene silencing affected one or both homeologous loci and was associated in part with cytosine methylation. Gene loss or methylation had occurred already in the F(1) intergeneric hybrid or in the allotetraploid, depending on the locus. The silenced/lost genes included rRNA genes and genes involved in metabolism, disease resistance, and cell cycle regulation. The activated genes with a known function were all retroelements. These findings show that wide hybridization and chromosome doubling affect gene expression via genetic and epigenetic alterations immediately upon allopolyploid formation. These events contribute to the genetic diploidization of newly formed allopolyploids.

SUBMITTER: Kashkush K

PROVIDER: S-EPMC1462064 | biostudies-other | 2002 Apr

REPOSITORIES: biostudies-other

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Gene loss, silencing and activation in a newly synthesized wheat allotetraploid.

Kashkush Khalil K Feldman Moshe M Levy Avraham A AA

Genetics 20020401 4

We analyzed the events that affect gene structure and expression in the early stages of allopolyploidy in wheat. The transcriptome response was studied by analyzing 3072 transcripts in the first generation of a synthetic allotetraploid (genome S(l)S(l)A(m)A(m)), which resembles tetraploid wheat (genome BBAA), and in its two diploid progenitors Aegilops sharonensis (S(l)S(l)) and Triticum monococcum ssp. aegilopoides (A(m)A(m)). The expression of 60 out of 3072 transcripts was reproducibly altere ...[more]

PMID: 11973318

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Project description:BACKGROUND: Alteration in gene expression resulting from allopolyploidization is a prominent feature in plants, but its spectrum and extent are not fully known. Common wheat (Triticum aestivum) was formed via allohexaploidization about 10,000 years ago, and became the most important crop plant. To gain further insights into the genome-wide transcriptional dynamics associated with the onset of common wheat formation, we conducted microarray-based genome-wide gene expression analysis on two newly synthesized allohexaploid wheat lines with chromosomal stability and a genome constitution analogous to that of the present-day common wheat. RESULTS: Multi-color GISH (genomic in situ hybridization) was used to identify individual plants from two nascent allohexaploid wheat lines between Triticum turgidum (2n=4x=28; genome BBAA) and Aegilops tauschii (2n=2x=14; genome DD), which had a stable chromosomal constitution analogous to that of common wheat (2n=6x=42; genome BBAADD). Genome-wide analysis of gene expression was performed for these allohexaploid lines along with their parental plants from T. turgidum and Ae. tauschii, using the Affymetrix Gene Chip Wheat Genome-Array. Comparison with the parental plants coupled with inclusion of empirical mid-parent values (MPVs) revealed that whereas the great majority of genes showed the expected parental additivity, two major patterns of alteration in gene expression in the allohexaploid lines were identified: parental dominance expression and non-additive expression. Genes involved in each of the two altered expression patterns could be classified into three distinct groups, stochastic, heritable and persistent, based on their transgenerational heritability and inter-line conservation. Strikingly, whereas both altered patterns of gene expression showed a propensity of inheritance, identity of the involved genes was highly stochastic, consistent with the involvement of diverse Gene Ontology (GO) terms. Nonetheless, those genes showing non-additive expression exhibited a significant enrichment for vesicle-function. CONCLUSIONS: Our results show that two patterns of global alteration in gene expression are conditioned by allohexaploidization in wheat, that is, parental dominance expression and non-additive expression. Both altered patterns of gene expression but not the identity of the genes involved are likely to play functional roles in stabilization and establishment of the newly formed allohexaploid plants, and hence, relevant to speciation and evolution of T. aestivum.

Dataset Information

Gene loss, silencing and activation in a newly synthesized wheat allotetraploid.

Publications

Gene loss, silencing and activation in a newly synthesized wheat allotetraploid.

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