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HvSWEET11b和HvSWEET15a基因是大麦发育过程中蔗糖释放的关键候选基因。我们还验证了它们在体外的蔗糖转运活性，并沿着主要的蔗糖分配途径定位了它们的表达。现在，我们已经培育出了甜味基因表达上调和下调的转基因大麦植株，并利用我们独特的分析(成像)管道计划了它们的全面表征。我们将应用磁共振成像(用于调查和监测活谷物中蔗糖的分配)、基于红外的显微光谱(用于高分辨率定量蔗糖测绘)、RNAS测序、代谢物分析和其他用于分析发育中的谷物。此外，对水稻的并行分子研究表明，OsSWEET11-1和OsSWEET15-1具有水稻籽粒fi定位所必需的所有特征。已经有了各自的单突变和双突变植株，并将在拟议的项目中进行分析。这种对比分析将解决大麦和大米是否利用相似或不同的蔗糖输送途径的长期争论。该项目将开发新的遗传资源，在全基因组关联扫描中研究甜味基因的遗传多样性。最终，将提供一个关于两种重要粮食作物籽粒蔗糖进口的机械论观点，以及改进谷类灌浆工程所需的知识库。

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.