Transcriptome and proteome wide identification of genes that are related to heterosis manifestion in maize seedling roots

杂种优势是指杂种的表现优于亲本自交系的平均水平，是由于相当数量的遗传位点相互作用的结果。了解杂种优势的重要一步将是这些位点的分子鉴定和表征。因此，我们建议从转录组和蛋白质组学角度对玉米幼苗根系中杂种优势相关基因表达和蛋白质积累进行广泛的表征。分析将包括四种不同自交系的六种组合，包括一种燧石/燧石（A × B）和一种凹痕/凹痕（C × D）群内杂交，以及这些自交系的四种可能的燧石/凹痕群间杂交（A × C, A × D， B × C和B × D）。这将允许在三种不同的杂交组合中研究每个基因的四个等位基因。在我们的实验中加入反向杂交将有助于研究亲本效应。在项目的初始阶段，将在表型和组织学水平上定量分析所选自交系和杂交种的早期根系发育。然后将在一个确定的发育阶段用所有六个互交的幼苗根进行微阵列实验。同样发育阶段的三个这些互惠杂交种也将受到蛋白质组学分析。我们的目标是确定在自交系和杂交系中差异表达的基因/蛋白质子集，并根据显性或超显性假设的遗传模型测试这些基因中的哪些基因表达。在这些差异表达基因中，我们希望找到相对表达水平与杂种优势程度相关的基因。在数据库中组织分析数据并将分子数据集成到建模框架中可能有助于预测适合未来杂交生产的自交系组合。总之，通过这种方法，我们希望对涉及杂种优势的复杂遗传网络的分子理解有所贡献。

Heterosis describes the superior performance of hybrids compared to the average of their parental inbred lines and is attributed to the interaction of a considerable number of genetic loci. A major step towards the understanding of heterosis will be the molecular identification and characterization of these loci. We suggest therefore a transcriptome- and proteome wide characterization of heterosis related gene expression and protein accumulation in roots of young seedlings of maize. The analyses will comprise six combinations of four different inbred lines including one flint/flint (A x B) and one dent/dent (C x D) intra-group cross and the four possible flint/dent inter-group crosses of these inbred lines (A x C, A x D, B x C and B x D). This will allow to study four alleles of each gene in three different hybrid combinations. Inclusion of reciprocal crosses in our experiments will allow to study parent of origin effects. In the initial phase of the project, early root development of selected inbred lines and hybrids will be quantitatively analyzed on the phenotypical and on the histological level. Microarray experiments will then be conducted with young seedling roots of all six reciprocal crosses at one defined developmental stage. The same developmental stage of three of these reciprocal hybrids will also be subjected to a proteomic analysis. Our objective is to identify a subset of genes/proteins which is differentially expressed in inbred lines versus hybrids and to test which of these genes are expressed according to the genetic models of the dominance or overdominance hypothesis. Among the differentially expressed genes we hope to identify genes whose relative expression level can be correlated with the degree of heterosis of a given hybrid. Organization of profiling data in databases and integration of the molecular data into a modeling framework might help to predict suitable inbred combinations for future hybrid production. In summary with this approach we hope to contribute to the molecular understanding of the complex genetic networks involved in heterosis.