Modulating seed size in oilseed rape

油料作物的种子为高价值脂肪酸和蛋白粉提供了一个综合的生产平台和精炼厂。芸苔属油菜（OSR）是北欧植物油的主要来源，具有最大限度地提高人类和牲畜营养产量和质量的巨大潜力，以及新型食品和非食品产品的多样化，包括生物可再生和第一代生物燃料。OSR是英国耕地轮作的一个重要和有利可图的部分，是一种近期作物，产量优化较差（英国平均约3.3吨/公顷），收获指数（收获生物量/总植物生物量）仅为小麦的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生长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年中成为温带地区的主要油料作物。然而，似乎没有理论上的发展限制，使重大进展，以增加种子大小，这应该有好处的表面积：体积比，加工性和作物建立。在过去的20年里，杂草状的塔勒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的内部运作的深入了解大多来自于它。2000年建立的拟南芥基因组的完整DNA序列使得在理解植物发育中单个基因的作用和功能方面取得了快速进展。拟南芥属于同一植物家族，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，使英国的主要作物受益。巴斯大学最近利用拟南芥进行的世界领先的研究已经确定，在这个物种中，有两种主要的发育机制可以操纵种子大小。这首先涉及胚乳大小的作用。胚乳相当于植物的胎盘，它从母体获得食物并将其传递给生长中的胚。使用各种遗传修饰延长胚乳的生长期产生更大的胚乳，其能够更好地从母体获得食物。结果是一个更大的胚胎。其次，增加珠被层内的细胞数量大大增加了最终的种子重量。珠被形成一个容器或袋，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，胚和胚乳的生长是为了填满可用的空间。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，最终导致更重的种子。我们期望从拟南芥研究中获得的许多信息与芸苔属作物种子有关。然而，我们需要检查类似的机制，因为芸苔属种子可以比拟南芥种子大400倍。在这个项目中，我们将结合联合收割机分析方法在拟南芥中完善，以研究在芸苔属种子大小的相对发展。我们将分配已知的变化，在芸苔属种子大小的具体发展机制，并将利用一些独特的实验资源来测试假设，类似的机制在较大的芸苔属种子。我们还将确定是否在拟南芥中确定的基因的位置有助于调节种子大小可能位于芸苔属染色体上的可预测的位置。我们获得的信息应极大地帮助植物育种家和生物学家开发适当的筛选方法，从芸苔属基因库中选择材料，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.