Functional and quantitative imaging study on maize kernel metabolism

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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.