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Regulation of peroxisomal metabolite carrier proteins

Subject Area Plant Physiology
Term from 2011 to 2025
Project identifier Deutsche Forschungsgemeinschaft (DFG) - Project number 196842819
 
Final Report Year 2023

Final Report Abstract

This final report describes the results of experiments planned as part of the proposal to study the regulation of the Arabidopsis peroxisomal NAD transporter PXN by phosphorylation. Possible phosphorylation sites in the Arabidopsis PXN protein were discovered by various proteomic approaches. We have expanded our studies to include other possible phosphorylation sites in our analysis. Initial in vitro NAD uptake experiments with recombinant PXN proteins reconstituted in liposomes indicated that phosphorylation at the predicted serine residues enhanced PXN activity. However, detailed analysis of recombinant PXN synthesized in a prokaryotic and eukaryotic cellfree system as well as in intact yeast cells yielded inconclusive results. Also, proteomic analysis of isolated peroxisomes from Ricinus seedlings did not identify any of the predicted phosphorylation sites or other post-translational modifications in the PXN protein. Based on these findings, we focused on a detailed phenotypic analysis of Arabidopsis mutants, in which the intracellular distribution of NAD within the plant cell is impaired due to the absence of mitochondrial and peroxisomal NAD carriers. These results have been published in three manuscripts. In addition, we were able to use the obtained proteomic data from Ricinus to reveal the metabolic interplay of peroxisomes, mitochondria, and peroxisomes in the mobilization of storage substances such as oil, proteins, and starch. This organellar network in germinating seedlings has been described in an accepted manuscript.

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