SWEETs: Mechanistic model of sucrose allocation in grains of barley and rice

蔗糖是种子生长和贮藏产物合成的主要碳源。我们之前的项目确定了HvSWEET11b和HvSWEET15a基因是发育中的大麦籽粒蔗糖释放的关键候选基因。我们还在体外验证了它们的蔗糖转运活性，并定位了它们在主要蔗糖分配途径上的表达。现在，我们已经培育出了SWEET基因表达上调和下调的转基因大麦植株，并计划利用我们独特的分析（成像）管道对其进行综合表征。我们将应用磁共振成像（用于测量和监测蔗糖在活谷物中的分配）、红外微光谱（用于高分辨率定量蔗糖制图）、rnas测序、代谢物谱分析等技术来分析发育中的谷物。此外，对水稻的同步分子研究表明，OsSWEET11-1和OsSWEET15-1具有水稻籽粒灌浆所必需的所有特征。不同的单突变株和双突变株已可用，并将在拟议的项目中进行分析。这种比较分析将解决长期以来大麦和水稻是否利用相似或不同的蔗糖输送途径的争论。该项目将利用新的遗传资源，在全基因组关联扫描中研究SWEET基因的遗传多样性。最终，对两种重要谷类作物籽粒中蔗糖的进口机理进行了研究，并为改良籽粒灌浆工程提供了必要的知识基础。

Sucrose is the main source of carbon for growth and storage product synthesis in seeds. Our previous project identified HvSWEET11b and HvSWEET15a genes as key candidates for sucrose release in developing barley grains. We also verified their sucrose transport activity in vitro and localized their expression along the main sucrose allocation route. Now, we have generated transgenic barley plants with up and down regulated expression of SWEET genes, and plan their comprehensive characterization using our unique analytical (imaging) pipeline. We will apply magnetic resonance imaging (for surveying and monitoring of sucrose allocation in the living grain), infrared-based microspectroscopy (for high resolution quantitative sucrose mapping), RNASequencing, metabolite profiling and others for the analysis of developing grains. Moreover, concurrent molecular studies on rice revealed that OsSWEET11-1 and OsSWEET15-1 show all the hallmarks of being essential for grain filling in rice. Respective single and double mutant plants became available, and will also be analysed in the proposed project. This comparative analysis will solve the long-standing debate whether barley and rice exploit similar or distinct sucrose delivery routes. The project will exploit new genetic resources to study the genetic diversity in SWEET genes in genome wide association scans. Ultimately, a mechanistic view on sucrose import in grains of two important cereal crops will be provided as well as a knowledge base required for engineering of improved grain filling in cereals.