Metabolic control of plant non-photosynthetic metabolism

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Non-photosynthetic metabolism fulfills important functions in plant biology. Glycolysis degrades sugars derived from photosynthesis and feeds cellular respiration to generate metabolic energy. Glycolysis and respiration also generate carbon molecules that serve as precursors for various plant biosynthetic pathways. Plants also use glycolytic and respiratory metabolisms to adapt to various biotic and abiotic stresses. While the world population is steadily growing, there is an increased need for agricultural resources, and in particular, crop plants. This situation will likely exacerbate with the impending climate change crisis expected to create a deterioration of agricultural productivity in many areas of the world. The rationale modification of plant metabolism by genetic engineering is a solution to generate new agricultural varieties adapted for the future needs of the human population. The use of this strategy nevertheless requires a good understanding of non-photosynthetic metabolism and its regulation. My research team addresses this problem by studying the regulation of enzymes in sugar and energy metabolism. One aspect of the research described in this proposal will focus on S-glutathionylation, a stable modification of protein cysteine thiol residues by the tripeptide glutathione, which can regulate enzyme activity. S-glutathionylation is promoted by oxidative stress, a frequent consequence of biotic and abiotic stresses. It also commonly targets enzymes of carbohydrate metabolism in photosynthetic cells. HQPs in my laboratory will identify S-glutathionylated proteins in Arabidopsis thaliana non-photosynthetic cell cultures and roots exposed to oxidative stress. They will also aim to identify and characterize the enzymes(s) that are involved in deglutathionylation, the removal of glutathione from a modified protein. They will furthermore study the regulation of specific enzymes in plant glycolysis and energy metabolism, which are targeted by S-glutathionylation. Another part of the proposed research concerns the characterization of nucleoside diphosphate kinases (NDPKs). The latter are multifunctional enzymes identified as metastasis suppressors in humans. Our recent work on NDPK1, the cytosolic plant NDPK isoform indicate that this enzyme plays an important role in the control of metabolic energy and the regulation of carbon fluxes between the starch and cellulose synthesis pathways. We will continue our characterization of NDPK1 by investigating its activity as a protein kinase. We will also initiate the study of a recently discovered NDPK, putatively localized in the endoplasmic reticulum. Its subcellular localization, regulation, and possible metabolic function will be characterized. In the long term, this research should provide crucial information for predictive metabolic modelization and metabolic engineering of future crop varieties.