Decoding gene expression in polyploid wheat

许多全球重要的作物都是多倍体，例如棉花、甘蔗、土豆和小麦。然而，多倍体基因组的调控是复杂的，因为大多数基因都有多个拷贝。我们对调控这些基因拷贝的分子机制了解有限。在本项目中，我们将利用最近小麦基因组学的革命，以小麦为模型系统，研究多基因拷贝如何被调控多倍体基因组。最广泛种植的小麦是六倍体面包小麦（Triticum aestivum），每个基因（同源）平均有三个高度相似的拷贝。每个基因的A、B和D同源物在编码序列中通常是95%相同的，并且可以是功能冗余的，即如果一个同源物发生突变，由于其他同源物的补偿，不会观察到表型效应。然而，我们不知道在同源物之间有多常见的功能冗余，也不了解控制冗余的分子机制。这种知识的缺乏限制了我们控制表型从而改进多倍体作物的能力。同源表达水平的研究是理解同源冗余的第一步，发现30%的小麦基因在a、B和D同源之间表现出不同的表达水平，这表明同源可能是非冗余的。我们的假设是，操纵同源基因相对表达水平的能力可能提供了一种减少功能冗余和更容易改变小麦表型的途径。因此，本项目将研究控制同源表达水平的机制，包括表观遗传和无义介导的衰变途径，以及它们对表型的影响。

Many globally important crops are polyploids, for example cotton, sugar cane, potato and wheat. However, the regulation of polyploid genomes is complicated because there are multiple copies of most genes. We have limited knowledge about the molecular mechanisms regulating these gene copies. In this project we will take advantage of the recent revolution in wheat genomics to study how multiple gene copies are regulated polyploid genomes using wheat as a model system. The most widely grown wheat is hexaploid bread wheat (Triticum aestivum) which has on average three highly similar copies of every gene (homoeologs). The A, B and D homoeologs of each gene are typically >95% identical within coding sequences and can be functionally redundant, i.e. if one homoeolog is mutated no phenotypic effect will be observed due to compensation by the other homoeologs. However, we do not know how common functional redundancy is between homoeologs or understand the molecular mechanisms controlling redundancy. This lack of knowledge limits our ability to control phenotype and hence improve polyploid crops. Homoeolog expression levels were studied as a first step towards understanding homoeolog redundancy and it was found that 30% of wheat genes show different expression levels between the A, B and D homoeologs suggesting that the homoeologs may be non-redundant. The hypothesis is that the ability to manipulate the relative expression levels of homoeologs may provide a route to reduce functional redundancy and more easily alter phenotypes in wheat. Therefore, this project will investigate the mechanisms that control homoeolog expression levels including epigenetic and nonsense-mediate decay pathways, and their effects on phenotype.