Photosynthesis Research

Engineering C3 plants with carbon concentrating mechanisms

The overall objective of this project is to engineer Arabidopsis thaliana, a C3 plant, to concentrate CO2 near the active site of the carbon fixing enzyme RuBisCO in order to favor carboxylation activity and improve photosynthetic efficiency. We will subsequently quantify changes in photosynthetic metabolism using isotope labeling and INST-MFA studies of leaves. No current isotope-based metabolic flux models exist for leaves, thus limiting understanding of photosynthetic plant metabolism and preventing rational metabolic engineering of plants for agricultural applications. We hypothesize that intracellular carbon dioxide levels are limiting photosynthetic efficiency in Arabidopsis, and we are testing this hypothesis by engineering plants that express heterologous proteins designed to "pump" CO2 into leaf chloroplasts.

Funding support: NSF EFRI (Sayre PI)
Graduate student: Lara Jazmin
Key collaborators: Dick Sayre (New Mexico Consortium), Doug Allen (Donald Danforth Plant Science Center)

Enhancing metabolic flux to photosynthetic bioproducts

One key application of isotopically nonstationary MFA (INST-MFA) is that it can be used to determine metabolic fluxes in autotrophic organisms using 13C tracers, an application that is not possible using conventional steady-state MFA. Working with collaborators at Purdue University, we have applied this approach to quantitatively map fluxes in the photosynthetic bacterium Synechocystis under fully autotrophic conditions (Young et al. Metab Eng 13:656–65, 2011). This is the first time that a comprehensive flux map has been constructed for an autotrophic system. Our future work will extend this approach to investigate strategies to increase production of biofuel compounds in engineered strains of cyanobacteria. These strategies will involve manipulating the endogenous circadian clock of cyanobacteria to enhance overall rates of carbon fixation, while engineering specific network nodes to divert flux into desired end products. By addressing current challenges of enhancing and redirecting flux in photosynthetic microbes, we aim to demonstrate the feasibility of converting energy from sunlight and carbon from CO2 directly into commercial chemicals.

Graduate student: Lara Jazmin
Key collaborators: Carl Johnson (Biology), John Morgan (Purdue), Doug Allen (Donald Danforth Plant Science Center)