Temperature, photosynthesis, and rubisco: biochemistry and physiology of land plant productivity in response to global change

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Photosynthesis is the process by which plants, algae, and some bacteria use solar energy to convert CO2 into biomass. Photosynthesis is the energetic basis of essentially all terrestrial and aquatic food webs, and produces food, fuel, shelter, and other materials that sustain human civilization. The basic metabolism is well known, but crucial aspects of how photosynthesis responds to the abiotic environment are unclear. For example, there are multiple hypotheses about why photosynthetic rates decline above a certain optimum temperature. Further, Rubisco, the enzyme that actually catalyses CO2 uptake, is a poor catalyst compared to most other enzymes, but our understanding of of the subtle relationships between its function and structure is in its infancy. Moreover, Rubisco has been characterized from very few species, and presently we model future crop and forest yields using constants that may be ill-suited to the purpose. My research asks questions about the temperature responses of photosynthesis, and the characteristics of Rubisco. My students and I will conduct detailed mechanistic analyses of photosynthesis at high temperatures, on plants with altered photosynthetic capacity. We use an array of physiological and biochemical techniques to comprehensively test hypotheses, within the context of established theoretical models. In the short-term, Rubisco studies will focus on how the expression of Rubisco-encoding genes changes with environment, or between closely related species with biochemically distinct Rubiscos. These studies will evaluate the possibility that plants optimise the enzyme for specific growth conditions. Toward the end of the grant cycle, we will determine the characteristics, particularly the temperature sensitivities, of key crop and boreal forest Rubiscos. The CO2 released by fossil fuel use is causing temperatures to rise and precipitation patterns to change. Photosynthesis links the atmosphere and biosphere, and my research expands our understanding of photosynthetic responses to global change, including the specific role of Rubisco.