Dr Sonia Evans in the Phillips Lab has solved the “pyruvate paradox” by showing Rubisco as the main source of pyruvate in chloroplasts.

The flow of carbon within a plant cell determines how fatty acids, amino acid and isoprenoids are synthesized from the three carbon precursor pyruvate.

For decades, scientists observed this carbon flux through precursors like phosphoenol pyruvate (PEP), but couldn’t account for the majority of pyruvate in illuminated chloroplasts.

In fact, Evans’ carbon flux analysis found that PEP was a third of what was required for pyruvate production. Using low O2 conditions and mutant analysis, Evans showed that the CO2 fixing enzyme Rubisco provides sufficient pyruvate through the MEP carbon pathway to resolve the pyruvate paradox.

The MEP pathway was thought to be a minor contributor to pyruvate production as MEP (methyl-d-erythritol-4-phosphate) was mainly seen as a precursor for isoprenoids in the plastid. Isoprenoids are used by plants in photosynthesis, defence and communication.

This research is published in Nature Plants as “Rubisco supplies pyruvate for the 2-C-methyl-d-erythritol-4-phosphate pathway“.

Evans has a life-long connection with plants and their uses, and earned a Provost Postdoctoral Fellowship to continue her research.

Congratulations, Dr Evans!