The processes which allow atmospheric carbon dioxide (CO2) to be captured and converted into sugars during photosynthesis happen inside plant cells, in the chloroplasts. These processes have significant limitations that could be improved, making plants more efficient at producing food.
Program 1 aimed to discover ways of minimising CO2 limitation of photosynthesis in plants through directed genetic manipulation and selection of crop plants. Professor Susanne von Caemmerer at ANU and Associate Professor Oula Ghannoum at WSU were the leaders of this Program.
Evolution has reduced plant limitations to capture carbon dioxide by three main ways: improving the inefficient CO2 fixing enzyme Rubisco; improving the diffusion of CO2; and implementing mechanisms for the concentration of CO2 around the active site of Rubisco.
Research areas and outcomes for this Program included:
Discovering how to produce better Rubisco enzymes and transplant them into the chloroplasts of crop plants. Rubisco is the most abundant protein on Earth and the most critical enzyme during photosynthesis. Professor Spencer Whitney led this project at ANU.
Key outcomes: We developed new plastome transformation and E. coli directed evolution tools for plant Rubisco bioengineering; demonstrated that Rubisco’s natural catalytic diversity can improve CO2 fixation under future climates; identified catalytic switches to increasing Rubisco activity in C3 and C4 crops; and established new directed evolution tools for high throughput evolution of any plant Rubisco.
Developing pathways to implement algal and cyanobacterial bicarbonate transporter-based CO2 concentrating mechanisms in plant chloroplasts. Professor Dean Price and Professor Murray Badger led this project.
Key outcomes: We established how cyanobacterial Rubisco interacts with the CcmM protein and how the cyanobacterial bicarbonate transporter SbtA is controlled.
Credit: Florian Busch, CoETP
Understanding CO2 diffusion pathways in leaves with an aim to developing strategies to minimise this limitation. This project was led by Professor Susanne von Caemmerer and Professor John Evans.
Key outcomes: We described the complete tobacco aquaporin gene family; revealed the relative contribution of the cell wall versus the membranes in restricting CO2 diffusion to understand how photosynthesis can be improved and where; discovered novel ways for manipulating crop water use efficiency and grain yield; demonstrated that altering CO2 fixation is crucial to build resilience in key agricultural crops to the impending challenge of climate extremes.
Developing strategies to enhance C4 photosynthesis. This project’s Chief Investigators include Professor Susanne von Caemmerer, Associate Professor Oula Ghannoum, Professor Robert Furbank and Professor John Evans.
Key outcomes: We established a transformation system for Setaria viridis to manipulate the C4 photosynthetic pathway; demonstrated that leaf width can be used as a high throughput selection trait in breeding programs.