Strategies of low temperature survival in Arabidopsis thaliana

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In the first year working on the project "Strategies of low temperature survival in Arabidopsis thaliana", we could prove multiple sub-cellular re-allocations of metabolites during cold acclimation by combining the methods of non-aqueous fractionation of compartments and quantitative metabolic profiling using GC-MS. Investigations on the metabolic mutants pgm and spsa1 that are defective in starch metabolism and strongly reduced in sucrose turnover, respectively, revealed strong evidence that a plastidial association of raffinose, cytosolic prolin and possibly the transfer of reducing equivalents and / or intermediates of phototranspiration between plastids and mitochondria are relevant for freezing tolerance. In a second phase of the project we want to expand these analyses to natural accessions of Arabidopsis that represent a broad spectrum of freezing tolerance. This shall allow drawing a "metabolic map" of cold acclimation with sub-cellular resolution. In particular, we want to follow up the evidence we obtained for exchange of aspartate / malate and glutamate / 2-oxo-glutarate for the transfer of reducing equivalents as well as ornithine / citrulline for the transfer of intermediates of photorespiration between mitochondria and plastids. n parallel, thermographic analysis of freezing events shall reveal whether Arabidopsis in general or specific natural accessions are able to tolerate ice formation in intracellular spaces, and whether certain metabolic patterns correlate with this ability. Modification of the content of relevant metabolites shall be used to alter freezing tolerance.