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PhD Proposal Seminar – Sonia Ehi-Eromosele (Phillips Lab)

June 10, 2021 @ 11:00 am - 11:30 am

Control of substrate supply in the chloroplast 2C-methyl-D-erythritol-4-phosphate pathway



The chloroplast 2C-methyl-D-erythritol-4-phosphate (MEP) pathway supplies precursors for terpenoid cofactors essential to photosynthesis and primary metabolism. In specialized contexts, it produces multitudes of high value secondary metabolites. This precursor pathway generates the universal terpenoid intermediates isopentenyl and dimethylallyl diphosphate (IDP and DMADP) from the central metabolic intermediates D-glyceraldehyde-3-phosphate (GAP) and pyruvate. While GAP is supplied via the Calvin-Benson cycle, the source of pyruvate in the chloroplast remains poorly understood. Pyruvate entering the MEP pathway may originate through the reimport of glycolytically derived phosphoenolpyruvate (PEP) from the cytosol due to downregulation of glycolysis in chloroplasts. Endogenous pyruvate production with contributions from the cytosolic pentose phosphate pathway (PPP) provides an alternative explanation. My dissertation aims to distinguish between these alternative carbon sources supplying the chloroplast MEP pathway and evaluate their relative contributions in Arabidopsis thaliana. This research line will provide insight to the following questions: What is the role of the PEP reimport shunt in MEP substrate supply in photosynthetic tissue? Can chloroplasts support endogenous pyruvate production? Can the Entner-Doudoroff pathway be engineered in plants to enhance pyruvate and GAP availability for the MEP pathway? To address the above questions, I will rely on 13C isotopic labeling studies in Arabidopsis mutants (cue1 or xpt2) deficient in a carbon import route. Mutant labeling time courses will be complemented by those of stable transgenic lines capable of pyruvate production in the chloroplast through constitutive expression of plastidic enolase and phosphoglycerate mutase. Mutants and transgenics altered in carbon metabolism or transport (and wild-type) will be examined using a 13CO2 kinetic labeling approach and mass spectrometry analysis. This research will provide a detailed understanding of substrate control for the plastid terpenoid precursor pathway.


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Meeting ID: 878 5873 7038

Host: Michael Phillips (michaelandrew.phillips@utoronto.ca)




June 10, 2021
11:00 am - 11:30 am
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