ERA-CAPS: Designing C4 breeding strategies using genetic enablers of C4 evolution

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Photosynthesis is the process used by all plants to synthesize food from sunlight, carbon dioxide and water. Whereas most plants use a mechanism of photosynthesis called C3, the most productive plants on the planet use a C4 mechanism (C3 and C4 respectively refer to three-and four-carbon molecules involved in photosynthesis). In addition to being more productive, C4 plants grow faster and require less water and fertilizer, suggesting it would be of value if more crop plants used the C4 mechanism. Converting C3 plants to C4 photosynthesis, however, has been frustrated by the fact that molecular mechanisms enabling C4 photosynthesis are poorly understood. In the land plants, C4 photosynthesis arose independently more than 60 times, and in the mustard family alone there are C3 plants, C4 plants and C3-C4 intermediaries. C3 species will be crossed with C3-C4 intermediaries, and genetic approaches will be used to help understand key genes and molecular mechanisms enabling the C4 trait. Knowledge gleaned will be used to engineer the C4 trait in C3 plants. Such a conversion will undoubtedly increase crop yields and reduce the need for inputs such as water and fertilizer with broad impact for society and agriculture. C4 photosynthesis is used by the most productive crops and native vegetation on the planet. However, the molecular mechanisms and the genetic architecture underlying this complex trait are poorly understood, impeding efforts to introduce this desirable trait into C3 crops. Recently, significant progress has been made both in understanding the mechanisms that prime species to evolve C4 photosynthesis as well as the evolutionary trajectories that then lead to the full C4 trait. Synthetic evolution and gene editing will be used to experimentally recapitulate the initial steps that establish the C4 trait. The hypothesis will be tested that establishment of a rudimentary photorespiratory carbon pump reduces the carbon dioxide compensation point and induces a primordial C4-like carbon cycle. Inter-species crosses will be conducted between C3 and C3-C4 intermediate Brassicaceae species to identify key anatomical and biochemical enablers of C4 evolution by quantitative genetics. Lastly, genome editing and wide intra-species crosses will be used to introduce C4 enablers into C3 Brassicaceaen models and crops such as oilseed rape. This project will train a postdoctoral fellow on the application of the latest gene editing and synthetic biological approaches to identify unknown components of C4 intermediacy and photosynthesis. Further, knowledge gained will be used to test whether components of C4 intermediacy and photosynthesis can be introduced into C3 plants, with the ultimate goal of increasing crop yields.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.