Global transgenerational gene expression dynamics in two nascent allohexaploid wheat lines analogous in genome constitution to common wheat (Triticum aestivum)

Alteration in gene expression accompanying initial stages of allopolyploidy is a prominent feature in plants, but its spectrum and model are highly idiosyncratic. We used multi-colour GISH to identify individuals from two nascent allohexaploid wheat lines between Triticum turgidum and Aegilops tauschii, which had a transgenerationally stable chromosomal constitution mimicking that of common wheat. We performed genomewide analysis of gene expression for these plants along with their parental species using the Affymetrix GeneChip Wheat Genome-Array. Comparison with parental species coupled with inclusion of empirical mid-parent values (MPVs) revealed two patterns of alteration in gene expression in the allohexaploid lines: parental dominance expression and nonadditive expression. Genes involved in each altered pattern could be classified into three distinct groups, stochastic, heritable and persistent, based on their transgenerational heritability and inter-line conservation. Whereas both altered patterns of gene expression showed a propensity of inheritance, identity of the involved genes is stochastic, consistent with the involvement of diverse Gene Ontology (GO) terms. Nonetheless, those genes showing nonadditive expression exhibited a significant enrichment for vesicle-function. Our results suggest global alteration in gene expression conditioned by nascent allopolyploidy likely play functional roles in stabilization and establishment of the newly formed plants, and consequential to evolution.

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