There is a clear need to increase crop productivity to feed our growing population. The enzyme RuBisCO is critical for the fixation of carbon dioxide into sugars in all plants, but its low efficiency makes it a major bottleneck in photosynthesis. To compensate for RuBisCO's low efficiency, plants with a photosynthetic process known as "C-3" (such as rice and wheat) devote a large fraction of their resources to producing the RuBisCO protein, which constitutes up to 50% of the total protein in their leaves. Unlike C3 plants, many algae have developed a means to drastically reduce the amounts of RuBisCO protein needed for efficient photosynthesis, by using a biophysical carbon concentrating mechanism (CCM). The CCM increases the carbon dioxide concentration within a subcellular compartment called the pyrenoid where RuBisCO is located, thus enhancing carbon dioxide assimilation with less RuBisCO protein. The ambitious goal of this program is to transfer the CCM from the green alga Chlamydomonas to the model C3 plant Arabidopsis, thus improving rates of carbon dioxide assimilation. The program will use a cutting-edge genome-wide screen to discover novel components of the algal CCM, including pyrenoid components. The physiological functions, localizations and physical interactions of known and newly-discovered components will be characterized by molecular and cell biological approaches, including electron microscopy and mass spectrometry. A modified RuBisCO will be developed and inserted into Arabidopsis to enable formation of a pyrenoid-like organelle. Known components and, progressively, key newly-discovered components, will be transferred to Arabidopsis and their impact on photosynthesis will be assessed. The process will be guided and supported by the development of advanced computational models. This transformative program represents a leap forward towards improving the photosynthetic efficiency of C3 crop plants, by introduction of a biophysical CCM from green algae. Additionally, the research will provide a much clearer molecular definition of the algal CCM, which is a fundamentally important yet poorly understood biological process. The research will provide undergraduate students opportunities to learn from a broad base of biological research.
