Sustainably increase crop yield
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The EC-funded project GAIN4CROPS is developing novel disruptive technologies to overcome one of the main constraints on photosynthetic efficiency: photorespiration, a process that reduces CO2 assimilation efficiency, and thus biomass yield and agricultural productivity.
In 5-years our project aims improve the efficiency of the most common photosynthetic metabolism in plants, the C3 metabolism, by following a stepwise approach. We will validate our findings in a set of model organisms of increasing cellular and anatomical complexity before moving to our final target: the sunflower.
Learn more about us
The project in numbers
A deeper view to our step-wise approach
Model organisms: from bacteria to sunflower
Introduce the natural C3-C4 pump
Engineer a C3 crop to operate the naturally occurring C3-C4 carbon-pump requires less complex anatomical and biochemical modifications than C4 metabolism and using solely genome editing and or wide crosses.
How we will do this? We will employ large-scale comparative genomics and systems biology approaches in closely related Helianthae species to identify features that enable the C3-C4 intermediacy. This information will be used for an innovative pre-breeding that mimics the initial steps in the natural evolution of C4. Further, we will explore whether these features can be introduced by intraspecies hybridization.
Maximize the use of cellular resources
C4 plants minimize photorespiration by increasing the CO2 concentration in a specific cell type, the bundle sheath cells. The drawback to this approach is the extra energy needed to transfer molecules back and forth from different cells.
We will develop more efficient synthetic C3-C4 carbon pump variants that are based on the effective intercellular transport of aspartate or malate while conserving cellular resources. This variant should interface photorespiration with the natural C4 module that efficiently concentrates CO2 in bundle sheath cells. These brand-new pathways use the cellular resources in a more efficient manner also by avoiding ammonia release.
Avoid CO2 release
Often metabolism that minimizes the deleterious effects of photorespiration still leads to the release of CO2, thus decrease carbon fixation rate and yield, just like in natural photorespiration.
In G4C we will develop a CO2-positive pump, that avoids releasing back the CO2, thus keeping it available for the plant metabolism.
We will develop two innovative photorespiration bypass routes that fix inorganic carbon, thus directly serving as supplementary CO2 fixation routes. We will develop the two alternative CO2- positive pumps based on C3-C4 metabolism and novel enzyme activities.
A multidisciplinary team
The science behind the project
The majority of plants (85%), including rice, wheat, soybeans and all trees, are C3 plants, which have no special features to combat photorespiration. They only use the Calvin Benson cycle for fixing the CO2 from the atmosphere. They have the disadvantage that in warm and dry conditions their photosynthetic efficiency suffers because of photorespiration.
C4 plants minimize photorespiration by separating initial CO2 fixation and the Calvin cycle in space, performing these steps in different cell types. This solution implies that the leaf anatomy is organized in specific cell compartments: the light-dependent reactions occur in the mesophyll cells (spongy tissue in the middle of the leaf) while the Calvin cycle occurs in special cells around the leaf veins, called bundle-sheath cells. In the latter, thanks to the active transfer of CO2, the environment has 10-120x more CO2 available, thus reducing RuBisCO’s activity on oxygen and the resulting photorespiration.
The C4 pathway is used in about 3%, percent of all vascular plants; some examples are crabgrass, sugarcane and corn. The drawback to C4 photosynthesis is the extra energy needed to transfer molecules back and forth from different cell types. C4 plants are common in habitats that are hot but are less abundant in areas that are cooler. In hot conditions, the benefits of reduced photorespiration likely exceed the associated costs.