Universality and regulation of gene expression complementation and its association with the phenotypic manifestation of heterosis in maize hybrids

玉米杂交种基因表达互补的普遍性和调控及其与杂种优势表型表现的关系

• 批准号: 417884885
• 负责人: Professor Dr. Frank Hochholdinger
• 金额: --
• 依托单位: Lehrstuhl für Crop Functional Genomics
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2019
• 资助国家: 德国
• 起止时间: 2018-12-31 至 2023-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/417884885?language=en
• 关键词: Universality; regulation; gene; expression; complementation

The observation that F1-hybrids are more vigorous than their parents is commonly referred to as heterosis or hybrid vigor. Maize, which provides the highest annual global kernel yield of all cereal species, is exclusively hybrid based in the major corn producing countries. The exploitation of hybrid vigor is considered as one of the most important innovations in modern agriculture because of its eminent economic importance. Nevertheless, the underlying molecular mechanisms remain largely enigmatic. In previous work, we observed an extreme form of gene expression complementation in hybrids for hundreds of genes that we designated single parent expression (SPE). Genes displaying such expression patterns are only active in one parent but always in the hybrid and thus are consistent with the dominance model of heterosis. As a consequence of these expression patterns, hybrids display hundreds of additionally active genes compared to their parental inbred lines. In the first part of this project, we will apply RNA-Seq to demonstrate that SPE complementation is universally observed and displays significant plasticity in belowground versus aboveground, seedling compared to mature and vegetative versus generative tissues in a distinct panel of genotypes. Subsequently, we will apply genomic evolutionary rate profiling to test the hypothesis that the inactive alleles in SPE patterns represent in general deleterious alleles, which would be in accordance with the dominance model of heterosis. In the second part of this project, we aim to understand the regulation of SPE complementation and its role in the phenotypic manifestation of heterosis. To this end we will take advantage of a maize recombinant inbred line population backcrossed to their parental inbred lines to identify key regulators of SPE genes by the determination of trans-eQTL regulatory networks via RNA-seq. Recombinant inbred lines backcrossed to their parents contain on average 50% heterozygous genes, whereas SPE patterns are expected to be reduced on average to only 75% in these genotypes compared to crosses of the two parental lines. Hence, in these populations the influence of heterozygosity and extreme dominance on heterosis can be separated. The variation of the number of SPE patterns in different recombinant inbred lines will allow testing their influence on phenotypic performance of the studied traits. Finally, high-resolution SNP markers obtained by the RNA-seq experiment will be used to identify loci underlying some of the heterotic traits quantified in this project by QTL mapping. In summary, these experiments will contribute to the mechanistic understanding of the molecular basis of heterosis and will provide knowledge that will facilitate the exploitation of heterosis in breeding and thus maize improvement.

观察到F1杂种比它们的亲本更有活力通常被称为杂种优势或杂种活力。玉米是所有谷物品种中全球籽粒年产量最高的，在主要玉米生产国中完全是杂交种。杂种优势的开发利用因其突出的经济意义而被认为是现代农业最重要的创新之一。然而，潜在的分子机制在很大程度上仍然是谜。在以前的工作中，我们观察到一种极端形式的基因表达互补的杂交数百个基因，我们指定单亲表达（SPE）。显示这种表达模式的基因只在一个亲本中有活性，但总是在杂种中，因此与杂种优势模型是一致的。作为这些表达模式的结果，与其亲本近交系相比，杂交种显示出数百个额外的活性基因。在本项目的第一部分，我们将应用RNA-Seq来证明SPE互补是普遍观察到的，并且在一组不同的基因型中，在地下与地上、幼苗与成熟和营养与生殖组织相比显示出显著的可塑性。随后，我们将应用基因组进化速率分析来检验SPE模式中的非活性等位基因通常代表有害等位基因的假设，这将符合杂种优势模型。在该项目的第二部分中，我们的目标是了解SPE互补的调节及其在杂种优势表型表现中的作用。为此，我们将利用玉米重组自交系群体与其亲本自交系回交，通过RNA-seq确定trans-eQTL调控网络来鉴定SPE基因的关键调控因子。与其亲本回交的重组近交系平均含有50%的杂合基因，而与两个亲本系的杂交相比，预期这些基因型中的SPE模式平均仅减少至75%。因此，在这些群体中，杂合性和极端显性对杂种优势的影响是可以分开的。不同重组自交系中SPE模式数量的变化将允许测试它们对所研究性状的表型表现的影响。最后，通过RNA-seq实验获得的高分辨率SNP标记将用于通过QTL作图来鉴定本项目中量化的一些杂种优势性状的潜在基因座。总之，这些实验将有助于从机理上理解杂种优势的分子基础，并将提供有助于在育种中利用杂种优势从而改进玉米的知识。