Lindsey Ching Rose Hills
Uncovering the Role of C4 Enzymes in C3 Photosynthesis under High-Stress Conditions
The vast majority of plants and crops, used both for food and fuel, utilize a type of photosynthesis in which the enzyme RuBisCO catalyzes the primary assimilation of carbon dioxide into sugar, termed C3 photosynthesis. However, certain plant lineages have evolved both biochemical and anatomical alterations, called C4 photosynthesis, that allow the enzyme PEP carboxylase to perform the primary assimilation event of CO2. C4 photosynthesizers have both higher photosynthetic efficiency and lower rates of an energy-intensive process called photorespiration relative to C3 plants, especially under high-stress conditions. As the climate continues to become more unpredictable, the benefits of the adaptations of C4 plants over C3 plants, in particular for food and fuel production, will become ever more critical.
A major hole in our understanding of how C4 photosynthesis evolved rests in the fact that while all the enzymes necessary to perform C4 photosynthesis are present in all C3 plants, their role in C3 photosynthesis is unknown. Using CRISPR-Cas9, I have successfully generated loss-of-function mutants in the enzymes necessary for C4 photosynthesis in the C3 model plant species Arabidopsis thaliana. I propose to look directly at photorespiration in my mutant lines to determine whether, under stress conditions, the enzymes of C4 photosynthesis already have an ancestral role in C3 plants in terms of limiting energy loss to photorespiration.