Key Laboratory of Molecular Epigenetics of MOE and Institute of Genetics and Cytology, Northeast Normal University, Changchun 130024, China.
BMC Biol. 2012 Jan 26;10:3. doi: 10.1186/1741-7007-10-3.
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.
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.
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.
由于异源多倍化导致的基因表达改变是植物的一个显著特征，但它的范围和程度尚不完全清楚。普通小麦（Triticum aestivum）大约在一万年前通过异源六倍体化形成，成为最重要的农作物。为了更深入地了解与普通小麦形成相关的全基因组转录动力学，我们对两个具有染色体稳定性和与现代普通小麦相似基因组组成的新合成异源六倍体小麦品系进行了基于微阵列的全基因组基因表达分析。
利用多色基因组原位杂交（GISH）鉴定了来自 Triticum turgidum（2n=4x=28；基因组 BBAA）和 Aegilops tauschii（2n=2x=14；基因组 DD）的两个新生异源六倍体小麦品系中的个体植物，它们具有与普通小麦（2n=6x=42；基因组 BBAADD）相似的稳定染色体组成。使用 Affymetrix Gene Chip Wheat Genome-Array 对这些异源六倍体品系及其来自 T. turgidum 和 Ae. tauschii 的亲本植物进行了全基因组基因表达分析。将这些结果与亲本植物进行比较，并包括经验性中亲值（MPV），结果表明，尽管大多数基因表现出预期的亲本加性，但在异源六倍体品系中鉴定出两种主要的基因表达改变模式：亲本优势表达和非加性表达。根据它们的跨代遗传和品系间的保守性，可以将参与两种改变表达模式的基因分为三个不同的组，即随机、遗传和持久。引人注目的是，尽管两种改变的基因表达模式都具有遗传倾向，但涉及的基因的同一性是高度随机的，与涉及不同的基因本体论（GO）术语一致。尽管如此，那些表现出非加性表达的基因显示出对囊泡功能的显著富集。
我们的研究结果表明，在小麦中，异源六倍体化导致了两种基因表达的全局改变模式，即亲本优势表达和非加性表达。这两种改变的基因表达模式而不是涉及的基因的同一性很可能在新形成的异源六倍体植物的稳定和建立中发挥功能作用，因此与 T. aestivum 的物种形成和进化相关。
