An evolutionary approach to optimising synthetic apomixis in cereal crops

我们建议研究植物种子介导无性生殖（无融合生殖）的关键基本过程，最终目的是在谷类作物中提供一个有效的系统。利用、控制和调节无融合生殖的能力有可能彻底改变杂交种子的繁殖，并通过使用更大范围的亲本植物来加速现代植物育种的实施。更广泛地说，提高我们对这一特性的理解也有助于消除水果和种子生产对授粉的需求，为开发生物技术工具提供了无限的机会。大多数开花植物通过雄性和雌性配子通过授粉和受精产生种子的过程进行有性繁殖。在授粉过程中，雄性配子转移到雌性胚珠，然后进行双受精，导致胚胎和胚乳的产生；以这种方式支持适应和进化的过程。然而，有大量的开花植物已经进化出了另一种无杂交模式，通过这种模式产生的种子产生的胚胎在遗传上与母体植物相同。种子介导的无融合生殖有多种形式，在禾草植物中最常见的一种依赖于规避雌性减数分裂（无减数分裂）和次级胚乳核受精而不使未减数的卵细胞受精（孤雌生殖）。控制这些过程的潜在遗传因素和机制尚未完全确定。发展对其中任何一种的有效理解本身都有潜在的价值，但综合考虑，它们提供了实现种子介导的无融合的可能性。我们建议部署和优化Khanday等人（2019）的概念验证水稻模型，以在大麦中实现合成无融合，这反过来将支持在其他商业上重要的复杂作物（如小麦）上的进一步工作。我们将设法改进水稻系统，目的是将无杂交后代的比例提高到商业上可行的水平。这将通过向前遗传学方法加以补充，利用无生殖的饲料草Eragrostis curvula作为基因靶标的来源，这也将在大麦中得到验证。该项目利用了大量的初步工作和数据，并利用了一个在植物繁殖、新育种技术、转化平台和应用于作物遗传学的生物信息学方面有着特别突出记录的团队的优势。鉴于NIAB和合作者最近在该领域取得的突破和进展，这是一个独特的机会，可以为了解无融合性做出重大贡献。

We propose to investigate the key fundamental processes underlying seed-mediated clonal asexual reproduction (apomixis) in plants with the ultimate aim of delivering an efficient system in cereal crops. The ability to deploy, control and modulate apomixis has the potential to revolutionise the multiplication of hybrid seeds and accelerate the implementation of modern plant breeding by enabling the use of a greater range of parental plants. More generally, advancing our understanding of this trait could also help to remove the need for pollination for fruit and seed production opening endless opportunities to develop biotechnology tools. Most flowering plants reproduce sexually by the production of male and female gametes through the processes of pollination and fertilisation generating seeds. During pollination male gametes transfer to the female ovules followed by a step of double-fertilisation which leads to the production of the embryo as well as the endosperm; in this way supporting the processes of adaption and evolution. There is, however, a large number of flowering plants that have evolved an alternative apomictic mode by which seeds are generated to produce embryos genetically identically to the mother plant. There are many forms of seed-mediated apomixis, the most common in grasses relies on the circumvention of female meiosis (apomeiosis) and the fertilization of the secondary endosperm nucleus without fertilising the unreduced egg cell (parthenogenesis). The underlying genetic factors and mechanisms governing these processes are not yet fully characterised. Developing a working understanding of either has potential value in its own right but considered together, they offer the possibility to implement seed-mediated apomixis.We propose to deploy and optimise the proof-of-concept rice model of Khanday et al. (2019) to deliver synthetic apomixis in barley, which will in turn support further work in other commercially important complex crops such as wheat. We will seek to improve on the rice system with the aim of raising the proportion of apomictic offspring towards commercially viable levels. This will be complemented by a forward genetics approach using the apomictic forage grass Eragrostis curvula as a source of gene targets which will also be validated in barley. This project draws on a large body of preliminary work and data, and on the strengths of a team with a particularly prominent track record in working with plant reproduction, new breeding technologies, transformation platforms, and bioinformatics applied to crop genetics. In the light of recent breakthroughs in the field and progress made by NIAB and collaborators, there is a unique opportunity to make a substantial contribution to the understanding of apomixis.