The Role of Vacuolar Sucrose cleavage in Abiotic stress Response of Arabidopsis thaliana

Jakob Weiszmann, Lisa Fürtauer, Wolfram Weckwerth, Thomas Nägele

Under abiotic stress influence, the stabilisation of primary carbohydrate and energy metabolism is essential for plant survival. Stress responses regarding involved metabolic pathways have been shown to not only comprise changes in metabolite levels but also affect subcellular translocation and signalling mechanisms [1]. Additionally, futile cycling of sucrose via sucrose cleavage and ATP-consuming hexose phosphorylation makes it difficult to intuitively derive conclusions about its regulation under stress conditions.

A non-aqueous fractionation method was applied to be able to determine subcellular concentrations of primary metabolites via gas chromatography coupled to a Time of Flight (ToF) mass spectrometer. Metabolite concentrations were used in a kinetic model of central carbohydrate metabolism consisting of ordinary differential equations (ODEs) describing the time dependent changes of sugar levels in the vacuole and the cytosol.
Nucleotide and phosphorylated sugar concentrations were measured by ion chromatography coupled to a triple quadrupole mass spectrometer.
To determine the physiological influence of cold and high light stress, chlorophyll fluorescence parameters were recorded to characterize the photosystem constitution.

Results and Discussion
In the presented study, a cold susceptible and a cold tolerant natural accession of Arabidopsis thaliana were exposed to a combined cold and high light stress revealing significant differences in the dynamics of sucrose and fumarate metabolism of these two accessions. Kinetic modelling of invertase-driven sucrose cleavage revealed differential subcellular invertase reprogramming, pointing to a substantial role of this enzyme in the initial stress response. The cold tolerant accession was shown to rely on sucrose cleavage in the vacuole during stress, while in the cold susceptible accession the cytosolic pathway of sucrose cleavage was more active. Finally, we applied a reverse genetic approach using a mutant being significantly impaired in vacuolar invertase activity, to approve the central role of this enzyme in stabilizing photochemical processes under freezing and high light conditions [2].

Innovative aspects
• Metabolic modelling on a subcellular scale
• Vacuolar sugar dynamics influence chloroplast performance under stress
• Natural accessions of Arabidopsis give insight in central stress responses

Research Platform Vienna Metabolomics Center, Large-Instrument Facility for Mass Spectrometry in Life Sciences
External organisation(s)
Ludwig-Maximilians-Universität München
No. of pages
Publication date
Austrian Fields of Science 2012
106044 Systems biology, 106057 Metabolomics, 106031 Plant physiology
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