Characterization of phosphofructokinase isoforms in Arabidopsis thaliana

• Applicant: Professorin Dr. Angelika Mustroph
• Subject Area: Plant Physiology ; Plant Biochemistry and Biophysics
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 493090432

Glycolysis is an essential metabolic pathway in plants since it initiates the energy production in plant cells without ongoing photosynthesis. It is therefore crucial for primary plant metabolism under optimal as well as under biotic and abiotic stress conditions which usually have a high energy demand. Despite its importance, several steps of glycolysis are still poorly understood. One crucial step of the glycolytic metabolism is the conversion of fructose-6-phosphate to fructose-1,6-bisphosphate, catalyzed by ATP-dependent phosphofructokinases (PFK) and possibly also by Pyrophosphate:fructose-6-phosphate phosphotransferase (PFP). The genome of Arabidopsis thaliana contains 7 and 4 genes coding for PFKs and PFPs, respectively. The contribution of each isoform to overall PFK activity in different organs and developmental stages is not known so far. Our previous research suggests that two isoforms, AtPFK1 and AtPFK7, are the major cytosolic isoforms, since a double mutant shows considerable growth defects. For one of the two plastidic isoforms, AtPFK5, we could recently demonstrate redox regulation by thioredoxin-f that point to an important function of this enzyme in plastid metabolism. However, a knockout of this isoform only had minor effects on plant metabolism. In this project we will create and verify higher-order PFK mutants and analyze their growth and metabolism as well as the transcriptomic responses to lowered PFK activity. In addition, these mutants might help solving the long-lasting question on the contribution of the reversible enzyme PFP to the glycolytic process in plants. If a genotype without detectable PFK activity is still viable, PFP might substantially contribute to glycolysis. Additionally, we will analyze how PFK isoforms are regulated at the protein level. PFK activity can be modified by substrate and product concentrations and other regulatory metabolites. We will also consider the different compartments of the plant cell since a difference between plastidic and cytoplasmic isoforms in terms of regulation has been described before. In this respect, the quaternary structure of PFKs will be evaluated, as well as its possible role in regulation of the in planta PFK activity. From this project we expect a new understanding of the phosphofructokinase reaction in the model plant Arabidopsis thaliana, which might be a basis for modification of the glycolytic activity in plants that could possibly affect growth and yield of crop plants.

• DFG Programme: Research Grants