Developing nutrient-enriched cereal grains with large embryos.

谷物由三种主要成分组成：谷壳、淀粉质胚乳和胚芽。胚芽（也称为胚）仅占谷物重量的一小部分（大麦和小麦中为2-3%），但与较大的胚乳相比，它富含营养。通常，谷物被加工成白色面粉，其中包括去除外壳和胚芽。然而，全谷物比白色面粉更富含纤维、营养素、维生素和矿物质，公众对全谷物制成的产品的需求越来越大。这是因为我们现在知道，吃全麦食物的人患几乎所有慢性疾病的风险都较低。我们的项目旨在增加胚芽大小，从而提高全谷物质量，以促进人类健康和动物营养。这是NIAB、剑桥和邓迪的詹姆斯赫顿研究所（JHI）的谷物科学家之间的合作。 我们的项目旨在确定在谷物驯化过程中发生的相对胚芽大小减少的因素。已经表明，在小麦的驯化过程中，胚乳的大小增加了，而胚芽的大小保持不变。通过比较野生和驯化谷物的集合，我们希望确定在驯化过程中相对胚芽大小何时以及如何变得次优。确定遗传因素，负责这将提供所需的工具，允许快速育种，以提高粮食质量。对栽培大麦和其他谷物（水稻和玉米）变体的研究表明，有可能大幅增加胚芽大小（尽管这伴随着胚乳大小的减少）。目前，已经发现了三个基因控制相对的胚芽大小。它们是：水稻和玉米中的巨胚（GE），玉米中的大胚1（BIGE 1）和大麦中的醇溶蛋白结合因子（PBF）。我们将研究这些基因及其工作的遗传和生化途径。我们的目标是找到一种方法来增加相对胚芽大小，而不会导致胚乳大小、籽粒大小或产量的有害下降。 在迄今已知的控制胚芽大小的三个基因中，PBF具有最大的商业潜力，因为它仅影响大麦籽粒发育，对植物生长没有任何不利影响。然而，伴随PBF功能降低的对胚乳大小的负面影响大于GE和BIGE变体。为了找到克服这种对产量不利影响的方法，首先我们将测试是否有可能使用遗传操作将PBF对胚芽的有利影响与对胚乳的不利影响分开。我们将生产出胚乳中具有功能性PBF蛋白但胚芽中缺乏功能性PBF的大麦植物。其次，我们将研究PBF的作用模式，以确定胚特异性和胚乳特异性靶基因。选择这些靶基因中的特异性变异将允许植物育种者优化相对胚芽大小。最后，我们将利用我们对大麦和其他谷物胚芽大小控制的知识，生产出营养价值更高的小麦。我们将通过选择在水稻、大麦和玉米中已知控制这一点的三个基因的变异来将最佳胚芽大小的性状转移到小麦中：GE、BIGE 1和PBF。我们将利用硬粒小麦/意大利面小麦和面包小麦中公开可用的种质资源来鉴定变异基因，然后将这些变异基因联合收割机组合在一起形成不同的组合。将对由此产生的大胚小麦进行评估，以提高谷物质量。这种方法提供了一种非转基因途径，以提供营养品质增强的小麦植物。

Cereal grains are composed of three main components: husk, starchy endosperm and germ. The germ (also called the embryo) accounts for only a small proportion of grain weight (2-3% in barley and wheat) but compared to the larger endosperm, it is rich in nutrients. Very often, cereal grains are processed to produce white flour which involves removing the husk and germ. However, whole grains are richer than white flour in fibre, nutrients, vitamins and minerals and there is an increasing public demand for products made from whole grains. This is because we now know that people who eat whole-grain foods have a lower risk of almost all chronic diseases. Our project aims to increase germ size, thus enhancing whole-grain quality for human health and animal nutrition. It is a partnership between cereal scientists at NIAB, Cambridge and at the James Hutton Institute (JHI) in Dundee. Our project aims to identify the factors responsible for the reduction in relative germ size that has occurred during the domestication of cereals. It has been shown that endosperm size has increased during domestication in wheat, whilst germ size has remained constant. By comparing collections of wild and domesticated grains we hope to identify when and how relative germ size became sub-optimal during the course of domestication. Identification of the genetic factors responsible for this will provide the tools needed to allow rapid breeding for improved grain quality. Studies of variants of cultivated barley and other cereals (rice and maize) have shown that it is possible to drastically increase germ size (although this is accompanied by a decrease in endosperm size). At present three genes have been discovered that control relative germ size. These are: GIANT EMBRYO (GE) in rice and maize, BIG EMBRYO 1 (BIGE1) in maize and PROLAMIN-BINDING FACTOR (PBF) in barley. We will investigate these genes and the genetic and biochemical pathways in which they work. Our aim is to find a way to increase relative germ size without causing deleterious decreases in endosperm size, grain size or yield. Of the three genes known thus far to control germ size, PBF has the most commercial potential as it impacts on barley grain development only, without any detrimental effects on plant growth. However, the negative effect on endosperm size that accompanies reductions in PBF function is greater than that seen with GE and BIGE variants. To find a way to overcome this unfavourable impact on yield, first we will test whether it is possible to separate the favourable effects of PBF on the germ from the unfavourable effects on the endosperm using genetic manipulation. We will produce a barley plant with a functional PBF protein in the endosperm but lacking functional PBF in the germ. Secondly, we will investigate the mode of action of PBF to identify germ-specific and endosperm-specific target genes. Selecting for variation specifically in these target genes will allow plant breeders to optimize relative germ size. Finally, we will build on our knowledge of the control of germ size in barley and other cereals to produce wheat with improved nutritional value. We will transfer the trait for optimal germ size to wheat by selecting for variation in the three genes known to control this in rice, barley and maize: GE, BIGE1 and PBF. We will use publicly-available germplasm resources in durum/pasta wheat and bread wheat to identify variant genes and then combine these together in different combinations. The resulting large-germ wheat will be assessed for improved grain quality. This approach provides a non-GM route to deliver wheat plants with enhanced nutritional quality.