Production of wheat lacking B-type starch granules

淀粉是谷物的主要成分，其功能特性对粮食的利用有着重要的影响。相当重要的是淀粉颗粒的大小和形状。在小麦、大麦、黑麦及其近缘的大多数野草中，有两种类型的淀粉颗粒，称为A型和B型。它们的大小不同，导致了双峰颗粒大小的分布，这在植物淀粉中是不寻常的，在其他牧草中也不存在，包括Brachypodium、燕麦、水稻和玉米。较小的B型淀粉颗粒对小麦和大麦的许多最终用途有负面影响。到目前为止，通过育种来减少或去除这些作物中的B-颗粒的尝试都失败了。这是由于品种间B颗粒含量缺乏遗传差异所致。然而，这一特征在山羊草(山羊草)物种之间有更大的差异，山羊草是包括面包小麦祖先在内的野草。缺乏B-粒的山羊草物种的存在表明，有可能将B-粒含量的变异引入到与之密切相关的作物物种中。该项目建立在我们之前的工作的基础上，我们在该工作中发现了一个控制山羊草B-型淀粉粒含量的主效QTL。我们的最终目标是鉴定和操纵控制小麦和大麦中B-颗粒含量的基因BGC-1。在这个项目中，我们将调查含有BGC-1的基因组区域的基因顺序，并将其与其他禾本科植物的基因顺序进行比较。如果有机会在我们的项目时间表内出现，我们将准备利用其他实验室正在进行的基因组学项目的最新进展来鉴定小麦和大麦中BGC-1的直系同源物，我们将开始使用RNAi和分蘖技术在这些作物中操纵BGC-1。在鉴定BGC-1之前，我们将开始利用现有的面包小麦品种Paragon的缺失系集合来培育缺乏B颗粒的突变小麦植株。以前，这个群体已经被成功地用来通过堆积基因缺失来产生具有新表型的小麦突变体。通过筛选跨越BGC-1区域的缺失，我们可以选择在三个小麦基因组中每一个基因组中都可能缺乏BGC-1的品系，然后通过重复几轮杂交和选择将这些品系堆叠到单个植株中。本项目将产生：1)BGC-1区域的精细图谱，可能鉴定山羊草中的BGC-1基因，以及该区域/基因与其他牧草的比较。2)小麦和山羊草的近等基因系，这将允许进行功能测试，以确定无B颗粒谷物的用途。此外，如果BGC-1被确定，小麦和大麦基因操纵品系的生产和/或缺乏B颗粒的分蘖突变体的生产将在该项目结束时进行。

Starch is a major component of cereal grains and its functional properties have a significant impact on grain utilisation. Of considerable importance is the size and shape of the starch granules. In wheat, barley, rye and most of their wild grass relatives, there are two types of starch granules, called A- and B-type. These differ in size, leading to a bimodal granule-size distribution that is unusual amongst plant starches and not found in other grasses, including Brachypodium, oats, rice and maize.The smaller, B-type starch granules have negative impacts on many end-uses of wheat and barley. So far, attempts to reduce or remove B-granules from these crops by breeding have failed. The reason for this is the lack of genetic variation in B-granule content between cultivars. However, there is much greater variation for this character between species of Aegilops (Goat Grass), wild grasses that include the ancestors of bread wheat. The existence of Aegilops species lacking B-granules suggests that it should be possible to introduce variation for B-granule content into the closely-related crop species.The project builds on previous work in which we identified a major QTL controlling the content of B-type starch granules in Aegilops. Our ultimate goal is to identify and manipulate the gene responsible for the control of B-granule content in wheat and barley, Bgc-1. In this project, we will investigate gene order in the region of the genome harbouring Bgc-1 and compare it with that in other grasses. If the opportunity arises within our project's timeline, we will be ready to use the latest developments from ongoing genomics projects in other labs to identify the orthologs of Bgc-1 in wheat and barley and we will begin to manipulate Bgc-1 in these crops using RNAi and TILLING technologies.Prior to the identification of Bgc-1, we will start to produce mutant wheat plants lacking B-granules using a pre-existing collection of deletion lines of a breadmaking wheat cultivar Paragon. Previously, this population has been successfully used to generate wheat mutants with novel phenotypes by stacking deletions of genes. By screening for deletions spanning the Bgc-1 region, we can select lines likely to lack Bgc-1 in each of the three genomes of wheat and then stack these into a single plant by repeated rounds of crossing and selection.This project will produce: 1) a fine map of the Bgc-1 region and possibly identification of the Bgc-1 gene in Aegilops and a comparision of this region/gene with those in other grasses. 2) near-isogenic lines of wheat and Aegilops that will allow functionality testing to determine the utility of B-granule-less grains. In addition, if Bgc-1 is identified, the production of genetically manipulated lines of wheat and barley and/or TILLING mutants lacking B-granules will be underway by the end of the project.