Steps Toward Engineering a Fully Functional Pyrenoid Carbon Concentrating Mechanism in Higher Plant Species

Abstract

Climate change and a rapidly growing world population threaten global agriculture and food stability. As temperatures change and natural disasters like droughts and floods become more common, it is critical to develop technologies that can make crops more robust, less wasteful, and more resistant to changes in climate. One way to achieve this is to target Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), the most abundant protein on the planet and the enzyme responsible for forming complex biological molecules out of atmospheric carbon. Rubisco binds to atmospheric CO2 during the Calvin-Benson-Bassham Cycle, a critical step in photosynthesis. Despite the high conservation of Rubisco across thousands of species, it lacks binding specificity and can also bind atmospheric O2 instead of CO2 in a process called photorespiration. This process is harmful to plants and limits the efficiency of overall photosynthesis. To deal with this problem, several species have evolved carbon concentrating mechanisms that create a high CO2/O2 ratio around Rubisco, promoting carbon fixation and preventing photorespiration. One such carbon concentrating mechanism is built around the algal pyrenoid. The pyrenoid is responsible for highly efficient photosynthesis in most types of green algae and constitutes over a third of global carbon fixation. By engineering the pyrenoid into plant chloroplasts, more efficient crops could be produced to combat the challenges presented to the agriculture industry by climate change. Here, we present a highly effective and rapid system for the transient expression and analysis of algal pyrenoid genes in Nicotiana benthamiana and investigate the expression of three essential pyrenoid components in plant chloroplasts.