Nutrient release by cellular disintegration in developing barley seeds

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Assimilates are delivered by vegetative organs, enter the maternal part of developing barley grains and are released to the filial tissues by processes related to cellular disintegration at maternal/filial boundaries. A major player associated to nutrient release for endosperm supply is the small Jekyll protein. Because ectopic expression of the protein immediately initiates cell death, Jekyll action in nourishing grain tissues has to undergo fine-tuned regulation. Here, highly specific and high affine anti-Jekyll recombinant antibodies will be created and used for immunoprecipitation of the Jekyll-protein complex. After precipitation and complex purification, co-precipitated proteins will be identified by mass spectroscopy. Transcript, metabolite and hormone profiling will be done in parallel in three different nourishing grain tissues (nucellus, nucellar projection, embryo-surrounding region) expressing Jekyll and being in close proximity to developing endosperm and embryo. A comparative study in wild type grains and grains with repressed Jekyll expression will identify processes tightly correlated to Jekyll action. Regulatory compounds depicted by both, profiling and immunoprecipitation/MS analysis will be compared to confirm results of the independent methods. We expect knowledge about interacting components regulating Jekyll activity in a development-specific manner. We plan delineation of metabolic regulation of assimilate release from the different nourishing tissues, furthermore 3-D modelling of the developing embryo region. The new knowledge leads to a deeper understanding of physiological processes determining economically important characters of the grain parts endosperm and embryo.