Improving germination performance through a mechanistic understanding of seed priming

该项目将解决改善种子发芽的重要农业问题，特别是对种子进行预处理以加强发芽过程。种子是可持续农业和粮食安全的基础，主要以谷物和豆类的形式提供全球大部分粮食。种子在作物繁殖中也起着至关重要的作用，最佳产量需要高活力的种子批次，提供快速、均匀的发芽和耐胁迫条件的幼苗建立。通过在种子萌发前对种子进行预处理，通常可以改善商业物种的萌发和幼苗建立。这个过程，称为启动，包括控制水合作用，以激活发芽前的过程，而不完成发芽。然而，迄今为止，启动的分子基础以及相关的启动种子寿命损失尚未得到很好的理解，但细胞修复过程可能起关键作用。在这个项目中，我们将揭示在启动中赋予活力增强的分子机制，并建立相关的种子寿命损失的遗传基础。这建立在我们最近的发现之上，即介导植物对DNA损伤的反应机制控制着萌发。在干燥的种子中，背景DNA损伤的积累是稳定的，在种子成熟、储存和萌发过程中，不利的条件加剧了这种损伤。这导致胚胎在种子再水化时经历极高水平的基因组压力。在植物恢复生长之前，需要高水平的DNA修复活性来逆转这种损害，因为修复过程的失败会导致遗传物质的严重突变，发育受损并最终导致植物死亡。对DNA损伤的感知导致萌发早期细胞信号程序的快速激活，其功能是延迟萌发，延长修复时间，或激活细胞死亡。由于启动功能可以逆转这种发芽延迟，我们假设DNA修复和损伤信号传导过程在启动机制中起核心作用。在这里，我们将使用遗传、生化和高通量分析方法来揭示基因组完整性与启动之间的分子联系，为种子启动增强种子萌发建立机制基础。灌浆后的种子储藏性降低，给种业造成了巨大的产量经济损失。这种寿命缩短的根本原因尚不清楚。然而，我们最近发现，染色体断裂修复缺陷的种子在启动后寿命大大降低。这一重要的新结果揭示了引种种子中DNA损伤增加与发芽势加速丧失之间的新联系。我们将在这些结果的基础上揭示引物种子寿命缩短的分子基础，确定对特定修复活动的需求，以减轻引物后货架寿命缩短的影响。此外，识别与寿命缩短相关的信号反应为揭示引种种子寿命缩短的潜在细胞原因提供了有力的方法。该项目的最终目标是通过调节这些DNA修复因子的活性，在启动后开发具有延长寿命的植物新品系。我们将测试潜在的关键因素，以遗传提高拟南芥和甘蓝种子发芽的恢复力，这是一种对英国农业重要的作物物种。这些方法将解决长期存在的问题，即许多蔬菜物种的种子在储存后发芽和建立不良，导致作物产量下降。总而言之，该项目将使我们能够应用基于植物应激反应知识的技术，提供高质量的种子，并支持可持续农业。

The project will address the important agricultural issue of improving seed germination, in particular in seeds that are pre-treated to enhance germination processes. Seeds underpin sustainable agriculture and food security, providing the majority of global food principally as cereals and legumes. Seeds also play essential roles in crop propagation, and optimal yields require high vigour seed lots that provide rapid, uniform germination and seedling establishment that is tolerant of stress conditions. Germination and seedling establishment are routinely improved in commercial species by pre-treatment of seeds prior to germination. This process, termed priming, involves controlled hydration to activate pre-germinative processes without completion of germination. However, the molecular basis of priming, and the associated loss of seed longevity in primed seeds, is not well understood to-date, but cellular repair processes are likely to have key roles.In this project, we will uncover the molecular mechanisms which confer vigour enhancement in priming, and establish the genetic basis for the associated loss of seed longevity. This builds on our recent discovery that the mechanisms that mediate responses to DNA damage in plants control germination. In dry seeds there is a steady accumulation of background DNA damage which is exacerbated by adverse conditions during seed maturation, storage and germination. This leads to extremely high levels of genome stress experienced by the embryo upon seed rehydration. High levels of DNA repair activity are required early in germination to reverse this damage before growth resumes, as failure in repair processes results in severe mutagenesis of genetic material, impaired development and ultimately death of the plant. Sensing of DNA damage leads to rapid activation of cellular signalling programmes early in germination that function to delay germination, allowing extended time for repair, or activate cell death. As priming functions to reverse this delay to germination, we hypothesise a central role for DNA repair and damage signalling processes in the priming mechanism. Here we will use genetic, biochemical and high throughput analytical approaches to reveal the molecular link between genome integrity and priming, establishing the mechanistic basis of seed priming for the enhancement of seed germination.Primed seeds display reduced storability, resulting in substantial yield economic losses for the seed industry. The underlying causes of this reduced longevity is unknown. However, we recently identified that seeds defective in the repair of chromosomal breaks display highly reduced longevity after priming. This important new result reveals a novel link between increased DNA damage in primed seeds with the accelerated loss of germination potential. We will build on these results to reveal the molecular basis for the reduced longevity of primed seeds, identifying the requirement for specific repair activities that mitigate reduced shelf-life post-priming. Furthermore, identifying the signalling responses associated with reduced longevity provides a powerful approach to reveal the underlying cellular causes of the short lifespan of primed seeds.The ultimate aim of this project is to develop novel lines of plants with improved longevity after priming through modulating the activity of these DNA repair factors. We will test the potential of key factors to genetically improve the resilience of seed germination in Arabidopsis and Brassica oleracea, a crop species important to UK agriculture. These approaches will address the long-standing problem that seeds of many vegetable species suffer from poor germination and establishment after storage, resulting in reduced crop yields. Taken together, the project will enable the application of technologies based on our knowledge of plant stress responses to deliver high quality seeds and support sustainable agriculture.