Modulating seed size in oilseed rape

油料作物种子为高价值脂肪酸和蛋白质粉提供了综合生产平台和精炼厂。甘蓝油菜(OSR)是北欧植物油的主要来源，具有巨大的潜力，可最大限度地提高人类和牲畜营养的产量和质量，使新型食品和非食品产品多样化，包括生物可再生能源和第一代生物燃料。作为英国耕地轮作的重要和有利可图的一部分，OSR是最近一种产量优化较差的作物(英国平均约3.3吨/公顷)，收获指数(收获生物量/植物总生物量)仅为小麦可实现产量的约65%。种子大小对OSR的产量、质量和盈利能力起着关键作用，并通过其对幼苗活力的贡献对作物形成的早期阶段产生辅助作用。许多作物的驯化伴随着收获器官相对大小的增加，但油菜种子的情况并非如此，因为它在过去30年里被用作温带地区的主要油料作物。然而，在增加种子大小方面取得重大进展似乎没有理论上的发展限制，这在表面积：体积比、加工性和作物建立方面应该是有好处的。在过去的20年里，杂草丛生的水芹物种拟南芥一直被全球植物研究界用作模式生物，我们目前对植物生长和发育内部机制的深入了解很大程度上是来自于这个模式生物。2000年建立的拟南芥基因组的完整DNA序列使人们在理解单个基因在植物发育中的作用和功能方面取得了快速进展。甘蓝属于同一个植物家族，也是最接近的作物物种，因此我们能够迅速利用这些基本信息中的大部分来造福于英国的一种主要作物。巴斯大学最近利用拟南芥进行的世界领先的研究证实，在这个物种中，有两种主要的发育机制可以控制种子的大小。这首先涉及到胚乳大小的作用。胚乳相当于植物的胎盘/它从母亲那里获得食物，并将这些食物传递给正在发育的胚胎。利用各种基因修饰延长胚乳的生长期，可以产生更大的胚乳，从而更好地从母亲那里获得食物。结果是一个更大的胚胎。其次，增加珠被层内的细胞数量会极大地增加最终种子的重量。珠被形成一个容器或袋子，胚乳和胚胎在其中发育，很像哺乳动物的子宫。我们的实验表明，胚胎和胚乳的生长可以填补可利用的空间。通过增加珠被的大小来提供更大的空间，再次使用遗传修饰来发育，导致更大的胚乳和胚胎，并最终产生更重的种子。我们预计，从研究拟南芥中获得的许多信息将与油菜作物种子相关。然而，我们需要检查类似的机制是否起作用，因为油菜种子可以比拟南芥种子大400倍。在这个项目中，我们将结合在拟南芥中提炼的分析方法来研究油菜种子大小的相对发育。我们将把油菜种子大小的已知变异归因于特定的发育机制，并将利用一些独特的实验资源来检验假设，即类似的机制在较大的油菜种子中起作用。我们还将确定在拟南芥中被识别为有助于调节种子大小的基因的位置是否可能位于甘蓝染色体上的可预测位置。我们获得的信息将极大地帮助植物育种者和生物学家开发适当的筛选方法，以从Brassica基因库中选择材料，用于以可预测的方式调节种子大小。

Seeds of oil crops provide an integrated production platform and refinery for high value fatty acids and protein meal. Brassica oilseed rape (OSR) is the primary source of vegetable oil in N.Europe, with huge potential to maximise output and quality for human and livestock nutrition, diversification of novel food and non-food products including biorenewables and first generation biofuels. An important and profitable part of the UK arable rotation, OSR is a recent crop poorly optimised for yield (UK average ~3.3 t/ha) with low harvest index (harvested biomass/total plant biomass) only ~65% of that achievable for wheat. Seed size plays a key role in the yield, quality and profitability of OSR, with ancillary effects on the early stages of crop establishment through its contribution to seedling vigour. Domestication of many crops has been accompanied by an increase in the relative size of the harvested organ, but this is not the case for the seeds of rape since it became adopted as the major oil crop in temperate regions in the past 30 years. However, there appears to be no theoretical developmental limit to making major advances to increase seed size, which should have benefits in terms of surface:volume ratio, processibility and crop establishment. The weedy thale cress species Arabidopsis thaliana has been used by the global plant research community over the past 20 years as a model organism, from which much of our current deep knowledge of the inner workings of plant growth and development has arisen. The complete DNA sequence of the Arabidopsis genome established in 2000 has enabled rapid advances to be made in understanding the role and function of individual genes in plant development. Brassicas are in the same plant family and the closest crop species, so we are able rapidly to make use of much of this fundamental information to benefit a major UK crop. Recent world-leading research at the University of Bath using Arabidopsis has established that there are two major developmental mechanisms by which seed size can be manipulated in this species. These involve firstly the role of endosperm size. Endosperm is the plant equivalent of the placenta / it obtains food from the mother and passes this to the growing embryo. Extending the growing period of the endosperm using various genetic modifications produces a larger endosperm that is better able to obtain food from the mother. The result is a larger embryo. Secondly, increasing the number of cells within the integument layers greatly increases final seed weight. The integuments form a vessel or bag within which the endosperm and embryo develop, rather like the womb of mammals. Our experiments suggest that the embryo and endosperm grow to fill the available space. Providing a larger space by increasing the size of the integuments, again using genetic modifications to development, results in a larger endosperm and embryo, and ultimately a heavier seed. We expect much of the information gained from studying Arabidopsis to be relevant to Brassica crop seeds. However, we need to check that similar mechanisms operate, since Brassica seed can be up to 400 times larger than Arabidopsis seed. In this project we will combine analytical approaches refined in Arabidopsis to study the relative development of seed size in Brassica. We will assign known variation in Brassica seed size to specific developmental mechanisms and will make use of some unique experimental resources to test hypotheses that similar mechanisms operate in the larger Brassica seeds. We will also determine whether the location of genes identified in Arabidopsis as contributing to modulation of seed size are likely to be located at predictable positions on Brassica chromosomes. The information we obtain should greatly assist plant breeders and biologists in developing appropriate screening methods for selecting material from the Brassica genepool with which to modulate seed size in a predictable manner.