Relationship between sink-induced N remobilisation and seed filling in barley

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High yield and grain quality can only be achieved at optimum supply of the seed with carbon and nitrogen assimilates. In barley, the ear-near photosynthesizing organs, flag leaf and glumes, are important for supplying the grain. During seed filling C and N compounds are remobilized from these organs and transported to filling grains. Understanding these processes can potentially contribute to crops with higher N-use efficiency. This project addresses the interactions between sink-induced N remobilization and grain filling in barley. We plan correlation and network analysis between transcript and metabolite profiles in order to identify associations between gene expression and metabolite concentrations at corresponding stages in flag leaves, glumes and grains. We intend to identify regulators (gene products, metabolites), which control remobilization, grain filling and its interactions. Amino acid transporters with a potential role establishing source (flag leaf, glume) and/or sink activity (grain) for N remobilization/grain filling will be functionally characterized and validated by RNAi approaches. We plan comprehensive analysis of available transgenic barley models to find out whether increased grain-sink strength can have positive impact on Nremobilisation efficiency. Metabolite/hormone analysis of the grain vascular bundle will be performed after micro-dissection during early to mid-grain filling. We intend to analyse dynamics of metabolites along development with the aim to identify those with a potential role signaling N demand of the grain to the source.