A pipeline for efficient recombination in wheat

小麦高效重组的管道

• 批准号: BB/W003317/1
• 负责人: Keith Edwards
• 金额: $ 25.53万
• 依托单位: University of Bristol
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2021
• 资助国家: 英国
• 起止时间: 2021 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=BB%2FW003317%2F1
• 关键词: pipeline; efficient; recombination; wheat

Bread wheat (Triticum aestivum) is a hexaploid cereal with accounts for 20 per cent of the calories and protein consumed by humans and is also an important source of vitamins and micronutrients. It is the largest crop in the UK, grown over 2M hectares, adding over £1.6Bn to the UK economy, with a value almost ten times that for processed wheat-derived products. Despite substantial increases during the green revolution, yields in recent years have plateaued and are now susceptible to decline due to the changes in global weather patterns, in particular increased temperatures. Additionally by 2050, the world's population is expected to rise to 8.9 billion leading to major pressure on resources. As a result of these combined factors there is an urgent requirement to improve wheat varieties through the use of novel approaches based on recent advances in biological knowledge to augment traditional methods of plant breeding. Wheat breeding harnesses the natural process of meiosis, a specialised cell division that leads to the formation of male and female gametes. During meiosis, recombination between the pairs of parental homologous chromosomes generates genetic variation through the formation of genetic crossovers. The progeny that arise are the screened for improvement in desired traits, for instance yield. In wheat, as in most higher organisms the number of crossovers that occur between the parental chromosomes during each meiotic division is low, typically 1-3 and in tends to occur in favoured chromosomal regions. In wheat and some other cereals, this crossover localization is extreme such that most crossovers occur in the distal region near the chromosome ends. As a result large regions of the chromosomes rarely recombine and in effect, these regions become inaccessible to researchers mapping and selecting agronomically important traits. Also it creates the problem of linkage-drag in the recombination-cold chromosome regions where undesirable variation cannot be separated from useful traits. Crossovers arise from the controlled repair of programmed DNA-double strand breaks (DSBs) that are introduced throughout the genome by the SPO11 protein complex. In plants, such as wheat, only around 2.5% of DSBs are repaired as crossovers with the remainder being repaired as non-crossovers. Nevertheless, the DSBs that are not repaired as crossovers are important to allow chromosome pairing and accurate chromosome segregation to form the male and female gametes Our analysis in wheat shows that although DSBs occur throughout the genome they initially form in the distal chromosome regions before appearing in the remaining chromosomal regions. Thus it would appear that most crossovers arise from the earlier forming DSBs, with the later forming DSBs repaired as non-crossovers. This raises the question of whether the repair fate of DSBs can be modified such that crossovers hitherto restricted to distal regions can be redistributed to recombination cold-regions? During the BBSRC sLola upon which this current project is based we used CRISPR-Cas9 gene editing to generate lines in which the A, B and D genomic copies of the SPO11-1 gene have been mutated. We now propose to capitalize on these gene-edited lines to develop an efficient pipeline to create wheat lines in which the level of SPO11-1 activity has been modulated. Specifically we will generate lines in which the number of DSBs and the rate at which they occur is modulated with the aim of modifying the dynamics and repair fate. Additionally, we will use a modified SPO11-1 protein that has been fused to a DNA binding protein-domain to re-target a proportion of DSBs to different chromosome sites with the aim of promoting crossover formation in normally recombination-cold regions. We anticipate this pipeline will provide the basis to maximise the genetic variation that can be accessed by breeders for crop improvement.

面包小麦(Triticum Aestivum)是一种六倍体谷物，占人类消耗的卡路里和蛋白质的20%，也是维生素和微量营养素的重要来源。它是英国最大的农作物，种植面积超过200万公顷，为英国经济增加了超过16亿GB的收入，价值几乎是加工小麦产品的十倍。尽管在绿色革命期间产量大幅增加，但由于全球天气模式的变化，特别是气温上升，近年来产量已经停滞不前，现在很容易下降。此外，到2050年，世界人口预计将增加到89亿，这将对资源造成重大压力。由于这些综合因素，迫切需要利用基于生物学知识最新进展的新方法来改良小麦品种，以加强传统的植物育种方法。小麦育种利用减数分裂的自然过程，减数分裂是一种特殊的细胞分裂，导致雄配子和雌配子的形成。在减数分裂过程中，亲本同源染色体对之间的重组通过形成遗传交叉而产生遗传变异。产生的后代是对所需性状的改进进行筛选，例如产量。在小麦中，就像在大多数高等生物中一样，在每次减数分裂过程中，亲本染色体之间发生的交叉次数很少，通常是1-3次，而且往往发生在有利的染色体区域。在小麦和其他一些谷物中，这种交叉定位是极端的，以至于大多数交叉发生在染色体末端附近的远端区域。因此，大片区域的染色体很少重组，实际上，研究人员在绘制和选择重要农艺性状时无法接触到这些区域。它还在重组冷染色体区域产生了连锁拖拽的问题，在这些区域中，不希望看到的变异与有用的特征无法分开。交叉产生于对程序性DNA双链断裂(DSB)的受控修复，这些双链断裂由SPO11蛋白质复合体引入整个基因组。在小麦等植物中，只有大约2.5%的DSB被修复为交叉，其余的作为非交叉修复。然而，没有被修复为交叉的DSB对于染色体配对和准确的染色体分离形成雄配子和雌配子是重要的。我们在小麦中的分析表明，虽然DSB存在于整个基因组中，但它们最初形成于染色体的末端区域，然后出现在剩余的染色体区域。因此，似乎大多数交叉产生于较早形成的DSB，而较晚形成的DSB被修复为非交叉。这提出了一个问题，DSB的修复命运是否可以被修改，以便迄今仅限于远端区域的交叉可以重新分配到重组冷区？在本项目所基于的BBSRC sLola期间，我们使用CRISPR-Cas9基因编辑来生成SPO11-1基因的A、B和D基因组拷贝发生突变的品系。我们现在建议利用这些基因编辑的品系来开发一种高效的管道来创造其中SPO11-1活性水平已经被调控的小麦品系。具体地说，我们将生成这样的线，其中DSB的数量和出现的速度被调制，目的是改变动力学和修复命运。此外，我们将使用已融合到DNA结合蛋白结构域的修改后的SPO11-1蛋白，将一定比例的DSB重新定位到不同的染色体位置，目的是促进正常重组冷区的交叉形成。我们预计，这条管道将提供最大限度地扩大遗传变异的基础，育种者可以利用这些变异进行作物改良。

项目成果

Identification, characterization, and rescue of CRISPR/Cas9 generated wheat SPO11-1 mutants.

• DOI: 10.1111/pbi.13961
• 发表时间: 2023-02
• 期刊: PLANT BIOTECHNOLOGY JOURNAL
• 影响因子: 13.8
• 作者: Hyde, Lucy;Osman, Kim;Winfield, Mark;Sanchez-Moran, Eugenio;Higgins, James D.;Henderson, Ian R.;Sparks, Caroline;Franklin, F. Chris H.;Edwards, Keith J.
• 通讯作者: Edwards, Keith J.