Functional and quantitative imaging study on maize kernel metabolism

玉米粒是世界上最大的谷物，其胚乳在灌浆过程中严重缺氧。这种缺陷(缺氧)需要在分子和生化水平上进行特定的适应。在之前的项目中，我们开发了一个建立和适应玉米胚乳中低氧的机械框架。我们发现了核内的一个与同化物分配相关的空洞网络，并确定了与氧气供应相互反应的代谢途径(基因、代谢物)。基于我们的发现和假设，我们构建了新的玉米遗传模型，其中涉及低氧信号/驯化(转录因子)、线粒体代谢(2-氧戊二酸脱氢酶)和糖裂解(山梨醇脱氢酶1)等基因的调控表达。这些靶标的调控有望引起能量、氧化还原和糖代谢的变化，这与籽粒的生物合成性能和库容量有关。这个新项目旨在探索这些目标的功能意义。具体地说，我们的目标是在结合使用磁共振成像和FTIR显微光谱进行代谢物成像的基础上，对各自的转基因和突变玉米植株进行全面的表征。此外，我们将应用代谢物和转录本图谱(通过LC/MS和RNAseq)来全面描述籽粒代谢的生物化学和分子特征。综合方法将允许评估选定的基因与玉米的生物合成能力和籽粒灌浆的相关性。最终目的是加强我们对主要粮食作物同化物利用和产量产生的了解。

Maize kernels are the largest cereal grains and their endosperm is severely oxygen deficient during grain fill. This deficiency (hypoxia) requires specific adaptations at the molecular and biochemical level. In the previous project, we developed a mechanistic framework for establishment of, and acclimation to hypoxia in the maize endosperm. We uncovered a void network inside the kernel, having relevance for assimilate allocation, and identified metabolic pathways (genes, metabolites) which reciprocally respond to oxygen availability. Based on our findings and hypotheses, we generated novel genetic maize models with modulated expression of genes involved in low-O2 signaling/acclimation (transcription factors), mitochondrial metabolism (2-oxoglutarate dehydrogenase) and sugar cleavage (sorbitol dehydrogenase 1). The modulation of these targets is expected to induce changes in energy, redox and sugar metabolism, with relevance for kernel biosynthetic performance and sink strength. This new project aims to explore the functional significance of these targets. Specifically, we here aim a comprehensive characterization of the respective transgenic and mutant maize plants based on the combined use of magnetic resonance imaging and FTIR microspectroscopy for metabolite imaging. In addition, we will apply metabolite and transcript profiling (via LC/MS and RNASeq) for full biochemical and molecular characterization of kernel metabolism. The integrated approach will allow an evaluation of the relevance of selected genes for biosynthetic capabilities and grain filling in maize. The ultimate aim is to enhance our understanding of assimilate usage and yield generation in major cereal crops.