Genetic and mechanical approaches to enhancing crop seed vigour

种子是绝大多数人类农业的起点和终点。全球每年的种子贸易额目前超过340亿英镑，生产和销售均匀快速发芽的高质量种子支撑着这个行业。种子在作物建立之前在田间经历一系列应力。这些包括低水应力和机械阻抗从紧凑的土壤。种子活力是指种子在广泛的环境条件下发芽和建立幼苗的能力，并定义了作物在田间定植的成功。这是产量的关键决定因素，因为没有植物导致没有最终产品可收获。改善作物的这一特性是农业产业的主要目标，然而，活力的潜在机制仍然知之甚少。植物细胞的生长是由内部膨压推动周围细胞壁的机械过程。当细胞周围的细胞壁变弱时，细胞会变大，并在内部膨压的作用下屈服。已经鉴定了编码分泌到细胞壁并改变其结构组成和强度的蛋白质的基因。这种蛋白质曾经被命名为膨胀蛋白，它的作用是疏松细胞壁结构，允许细胞生长。在没有细胞分裂的情况下，种子到幼苗的转变完全通过细胞膨胀来驱动。产生足以抵消外部应力的机械力的能力定义了幼苗在广泛的环境条件下建立的能力，并因此具有活力。增加扩展蛋白的表达使得能够在通常限制该过程的胁迫条件下建立幼苗。因此，种子活力可以被认为是机械驱动的农艺性状，并且扩展蛋白表达的控制是目标。该项目采用跨学科的方法来揭示种子到幼苗过渡的遗传因素和机械基础，以及种子活力。我们以前确定的蛋白质，代表高置信度的候选调控因子的expansin基因表达。增加扩展蛋白基因的表达可以增加种子活力，使这些遗传目标增强种子活力。这些基因将在模式植物系统拟南芥中进行探索。这些发现将被扩展到提高作物品种甘蓝种子活力。将在不同的芸苔属植物中鉴定新表征的活力基因内的突变。与工业合作伙伴先正达一起，这些新的芸苔属种子的活力将得到表征。这将导致品种的鉴定，可直接用于育种计划，以提高幼苗建立，田间作物性能和产量。我们以前已经表明，细胞的大小，形状和排列可以影响种子萌发的早期阶段，以响应生长促进基因的表达，如expansin。这一观察结果强调了机械对植物生长的限制。然而，这些限制如何影响幼苗的生长仍然是未知的。理解种子到幼苗转变的机械基础对于理解作物在田间的建立和种子活力至关重要。利用三维图像分析和机械建模相结合的方法，将建立生长促进基因表达与幼苗生长之间的关系。通过这种方式，将揭示幼苗形成和种子活力的机械基础。提高芸苔属植物种子活力将在这一快速气候变化时期提高作物产量和粮食安全。该项目的研究结果可能会反过来扩展到其他作物物种。

Seeds are the start and end point for the vast majority of human agriculture. The annual global seed trade is currently valued at over £34 billion, and the production and sale of high quality seeds which germinate uniformly and rapidly underpin this industry. Seeds experience a range of stresses in the field prior to crop establishment. These include low water stress and mechanical impedance from compact soils. Seed vigour refers to the ability of seed to germinate and establish seedlings across a wide range of environmental conditions, and defines the success of crop establishment in the field. This is a key determinant of yield as the absence of a plant leads to no end product to harvest. Improving this trait in crops is a primary goal of the agricultural industry, however the underlying mechanisms of vigour remain poorly understood.The growth of plant cells is a mechanical process driven by internal turgor pressure pushing against the surrounding cell wall. Cells get bigger when the surrounding cell wall is weakened and yields in response to internal turgor. Genes which encode proteins that are secreted to the cell wall and modify its structural composition and strength have been identified. Once such protein is named expansin, and acts to loosen cell wall structures, permitting cell growth.The seed to seedling transition is driven exclusively through cell expansion in the absence of cell divisions. The ability to generate of mechanical force sufficient to counteract external stresses defines the ability of a seedling to establish across a wide range of environmental conditions, and hence be vigorous. Increasing the expression of expansin enables seedling establishment under stress conditions which normally limit this process. Seed vigour may therefore be considered a mechanically driven agronomic trait and the control of expansin expression a target. This project takes an interdisciplinary approach to uncover the genetic factors and mechanical basis of the seed to seedling transition, and seed vigour. We previously identified proteins which represent high confidence candidate regulators of expansin gene expression. Increasing expansin gene expression can increase seed vigour making these genetic targets to enhance seed vigour. These genes will be explored in the model plant system Arabidopsis. These findings will be extended to enhance seed vigour in the crop species Brassica oleracea. Mutations within newly characterized vigour genes will be identified in different Brassica plants. Together with industrial partner Syngenta, the vigour of these new Brassica seeds will be characterized. This will lead to the identification of varieties which can be used directly in breeding programs to enhance seedling establishment, field crop performance and yield. We have previously shown that the size, shape and arrangement of cells can influence the early stages of seed germination in response to growth-promoting gene expression, such as expansin. This observation highlighted the presence of mechanical constraints on plant growth. How these constraints affect the growth of seedlings however remains unknown. Understanding the mechanical basis of the seed to seedling transition is of central importance to understanding the establishment of crops in the field and seed vigour. Using a combination of 3D image analysis and mechanical modelling, the relationship between growth promoting gene expression and seedling growth will be established. In this way the mechanical basis of seedling establishment and seed vigour will be uncovered.Enhancing Brassica seed vigour will increase both crop yields and food security during this period of rapid climate change. The findings in this project may in turn may in turn be extended to other crop species.