“Can we improve maize photosynthesis and resistance to chilling stress by over expressing a protein from Miscanthus?”
As the demand for maize increases and the growing season is shifted earlier by the changing climate, the need to increase the growth efficiency of maize lends urgency to the process of scientific development in maize agricultural practice. Previously, the Stern lab was able to increase Rubisco content in maize by overexpressing the large and small subunits of rubisco (LSSS) together with rubisco assembly factor 1 (RAF1), a chaperone that aids rubisco assembly. Although the RAF1-LSSS overexpressing transgenics did have a higher rate of carbon assimilation, the increase did not match the larger increase in Rubisco content. This finding suggests that there could be another rate limiting step in the C4pathway preventing carbon assimilation from increasing, potentially the enzyme PPDK. This summer, I worked with an antibody designed to bind to both Miscanthus and Maize PPDK equally so that Miscanthus PPDK overexpression could be visualized using immunoblot analysis. I also ran a chilling stress trial on maize overexpressing LSSS, RAF1, and PPDK from Miscanthus, taking phenotype measurements and photosynthesis measurements using the LI-COR. Results suggest that using protein overexpression to improve photosynthesis and resistance to chilling stress is a promising route towards improving maize photosynthesis. However, overexpressing PPDK may not be as impactful as we had hypothesized. Future experimentation will repeat the chilling stress trial with more plants, and with transgenic maize overexpressing photosynthesis enzymes from other species and from other steps in the C4 cycle.
With help from my amazing mentor Elena Michel, I was able to see both sides of the plant sciences by working with small-scale protein biochemistry and by seeing the impact of these biochemical differences on the macro scale of plant phenotype. Through these last 10 weeks, I have gained confidence in my ability to plan and execute experiments while learning more about the fundamental aspects of conducting plant science research. I am excited to apply to graduate school in biochemistry or plant sciences this fall and will take with me a renewed and more informed passion for applying my background in molecular biology to plants.