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

杂种优势是指杂交种的表现优于其亲本自交系的平均水平，并归因于相当数量的遗传座位的交互作用。了解杂种优势的重要一步将是对这些基因座的分子鉴定和表征。因此，我们提出了一个转录组和蛋白质组广泛的杂种优势相关基因表达和玉米幼苗根中蛋白质积累的特征。分析将包括四个不同自交系的六个组合，包括一个火石/火石(A×B)和一个凹陷/凹陷(C×D)组内杂交，以及这些自交系的四个可能的火石/凹陷组间杂交(A×C、A×D、B×C和B×D)。这将允许研究三个不同杂交组合中每个基因的四个等位基因。在我们的实验中加入正反交将使我们能够研究起源的亲本效应。在项目的初始阶段，将从表型和组织水平上对选定的自交系和杂交种的早期根发育进行定量分析。然后，在一个确定的发育阶段，对所有六个正反交组合的幼苗根进行基因芯片实验。这些相互杂交的三个相同发育阶段的后代也将接受蛋白质组学分析。我们的目标是找出在自交系和杂交种中差异表达的基因/蛋白质的子集，并根据显性或超显性假说的遗传模型来检验这些基因中的哪些是表达的。在差异表达的基因中，我们希望找出其相对表达水平与某一杂交种杂种优势程度相关的基因。在数据库中组织概况数据，并将分子数据整合到建模框架中，可能有助于为未来的杂交生产预测合适的近交系组合。综上所述，我们希望通过这种方法有助于从分子水平上理解涉及杂种优势的复杂遗传网络。

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.