Impact of intracellular organelle positioing on metabolic performance and stress tolerance of Arabidopsis plants

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Plant central metabolism is particularly flexible and reflects the need of plants to regularly modify their own internal physiology in response to developmental and environmental changes. While metabolic modelling has generated an understanding of the plant metabolic network, the strategies to regulate and allocate fluxes are not understood sufficiently well to account for the observable metabolic versatility of plants. At the posttranslational level, small molecule interaction, posttranslational protein modifications, and dynamic physical protein associations underpin current concepts of the regulation of metabolic fluxes. One of the oldest concepts of metabolic control, however, is compartmentation of plant metabolism into different organelles. The organelles themselves are mobile and their positioning relative to another is regulated and responsive to external conditions. Here, we aim to test the hypothesis that organelle positioning, and the generation of metabolic nano-domains structure the cellular metabolic landscape, support efficiency, and provide a novel layer of regulation. Combining the complementary expertise of three labs, we use a synthetic approach to manipulate and monitor the positioning of mitochondria and chloroplasts within Arabidopsis cells. We will alter the stability of a recently discovered glycolytic metabolon that physically links chloroplasts and mitochondria. We will further control organelle associations inducibly using the genetically encoded SpyCatcher system. To counteract interaction, we will anchor mitochondria and chloroplasts to different cellular membrane systems. To explore the significance of organelle positioning on cellular metabolism and plant performance we will employ advanced metabolite profiling, flux analyses and genetically encoded biosensors as well as phenotypic analyses, under different states of photosynthetic and photorespiratory metabolism. We will further immobilize protein biosensors on the surface of the organelles and other membranes to assess how organelle positioning and association shape metabolic gradients and nano-environments. The significance of dynamic structural organisation of plant cell organelles to adjust metabolic performance will be established.