Physiological function of nucleoside / nucleobase transport and catabolism

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In humans nucleoside transporters execute diverse functions, inter alia through interaction with purinergic receptors. In addition, nucleoside analogs are used to treat cancer. In plants, Equilibrative Nucleoside Transporter 1 (ENT1) function was found to be critical for pollen development, seed germination and maintaining the overall nucleotide balance. We propose to unravel the physiological reason leading to the observed phenotype in more detail. A focus will be on the question to what extend ENT1 function is involved in extracellular ATP signalling. Unexpectedly, ENT1 activity was found to be connected to vacuolar RNA metabolism. Therefore, this aspect shall be highlighted by analyzing vacuolar RNA (contents, nature of RNA, import mechanism) in Arabidopsis. In addition, Barley will be introduced as model system in our lab with respect to vacuolar RNA metabolism. Further aspects of the proposed work are related to nucleoside catabolism. In the last funding period novel proteins in this pathway could be identified. Among these, the extracellular nucleoside hydrolase NSH3 and the plastidic uracil importer Pluto have so far only been analyzed preliminary. A more detailed analysis of the impact of these proteins will be performed to complete our understanding of extracellular and intracellular nucleoside catabolism.