Sensing and retrograde signaling of mitochondrial metabolic states in plants

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The autotrophic and sessile nature of plants imposes unique demands on their metabolism, and consequently the metabolic network of plants is among the most complex of any organism. To adapt to often rapidily changing environmental conditions the capacity of the metabolic network has to be dynamically adjusted and ‘rewired’ in a way that it is tailored to meet exactly the energy and metabolic demands of the cell at any given moment in time. Plant mitochondria are key players in the cellular metabolism providing the cell with ATP, reducing-power, carbon intermediates and various other important metabolites. The dynamic adjustments of the mitochondrial proteome require signals that sense the status of the organelle and communicate it back to the nucleus. This is referred to as retrograde signaling. In the case of plants, the interpretation of retrograde signals is further complicated by the occurrence of retrograde signals from other organelles such as the plastid. Thus, specificity in signal recognition is a prerequisite. This project aims to investigate the evolutionary conserved process of cell-specific recognition of metabolites in connection with mitochondrial retrograde signaling. Own results demonstrate that perturbations in cellular concentrations of organic acid levels resulting from alterations in tricarboxylic acid cycle activities have a major impact on nuclear gene expression. The aim of this project is to investigate and dissect this mitochondrial retrograde signaling pathway to identify the underlying regulatory mechanisms and components (genes, proteins and metabolites). The approach chosen to tackle this question is based on state of the art genetic and biochemical techniques including expression- and promoter analysis, a forward-genetic screen, the analysis of posttranscriptional modifications and the identification of novel metabolite-binding proteins and signal metabolites.