Improving germination performance through a mechanistic understanding of seed priming

该项目将解决提高种子发芽的重要农业问题，特别是经过加强发芽过程的预处理的种子。种子是可持续农业和粮食安全的基础，提供了全球大部分粮食，主要是谷类和豆类。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、均匀的萌发和耐受逆境条件的成苗。在商业树种中，发芽和成苗通常是通过在发芽前对种子进行预处理来改进的。这个过程被称为引发，包括受控的水合作用，以激活萌发前的过程，而不是完成萌发。然而，到目前为止，引发的分子基础以及引发种子寿命的相关损失还不是很清楚，但细胞修复过程可能具有关键作用。在这个项目中，我们将揭示引发增强活力的分子机制，并建立与种子寿命损失相关的遗传基础。这建立在我们最近的发现基础上，即调节植物对DNA损伤的反应的机制控制着种子的萌发。在干燥的种子中，背景DNA损伤不断积累，在种子成熟、储存和萌发过程中的不利条件会加剧这种损伤。这导致胚胎在种子复水时经历极高水平的基因组压力。在萌发早期需要高水平的DNA修复活动，以在恢复生长之前扭转这种损伤，因为修复过程的失败会导致遗传物质的严重突变，损害植物的发育，最终导致植物死亡。对DNA损伤的感知导致在萌发早期迅速激活细胞信号程序，这些程序的功能是推迟萌发，延长修复时间，或激活细胞死亡。由于启动功能逆转了这种萌发延迟，我们假设DNA修复和损伤信号过程在启动机制中发挥核心作用。在这里，我们将利用遗传学、生化和高通量分析方法来揭示基因组完整性与引发之间的分子联系，为种子引发促进种子萌发奠定机理基础。这种寿命缩短的根本原因尚不清楚。然而，我们最近发现，在修复染色体断裂方面存在缺陷的种子，在启动后寿命会大大降低。这一重要的新结果揭示了引发种子中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发种子寿命缩短的分子基础，确定特定修复活动的要求，以减轻引发后货架期的缩短。此外，识别与寿命降低相关的信号反应为揭示引发种子寿命短的潜在细胞学原因提供了一个强有力的途径。该项目的最终目标是通过调节这些DNA修复因子的活性来培育引发后寿命延长的植物新品系。我们将测试关键因素在遗传上提高拟南芥和甘蓝种子萌发弹性的潜力，这两种作物对英国农业很重要。这些方法将解决长期存在的问题，即许多蔬菜品种的种子在储存后发芽和形成不良，导致作物减产。总而言之，该项目将使我们能够应用基于我们对植物胁迫反应的知识的技术来交付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.