Proteomic approaches and live-cell imaging reveal unique aspects of delivery of cellulose synthase complexes to the plasma membrane

Understanding how plant cells synthesize cellulose not only lays the scientific foundation for using genetic tools to modify plant cell walls for advances in sustainable energy but also provides insights into fundamental questions regarding how plant cells control expansion and shape. This project aims to utilize a combination of quantitative live-cell imaging, quantitative proteomics, and functional genetics to investigate how plant cells couple exocytosis and endocytosis to regulate the abundance of cellulose synthase at the plasma membrane—a process that remains largely unexplored. These findings will enhance knowledge of both cell wall biosynthesis and the mechanisms underlying plant cell growth. Furthermore, the project will create research opportunities for undergraduate students. By tailoring research projects to various undergraduate research programs, this initiative will attract talented students and prepare them for graduate education and academic careers. Additionally, the project will include a hands-on research workshop for local high school students and their teachers at Pennsylvania State University, aiming to inspire interest in the biological sciences. The ability to produce renewable energy is crucial for both the economy and the environment, with cellulosic biomass expected to be a key source for biofuel production. Cellulose microfibrils are synthesized at the plasma membrane by a protein complex known as the cellulose synthase complex (CSC), which converts sugar molecules into energy-rich crystalline cellulose, the most abundant biopolymer on Earth. Since cellulose synthesis occurs exclusively at the plasma membrane, understanding how CSCs are trafficked to the cell surface is essential. The abundance of CSC at the plasma membrane is tightly regulated. Cellulose synthase proteins can remain stable for over 48 hours in vivo, and their regulation relies on exocytosis, endocytosis, and recycling, rather than protein turnover. Unlike mammalian and yeast systems, where exocytosis and endocytosis are well-studied, cellulose synthase represents a plant-specific cargo protein, making it a unique subject of investigation. The principal investigator’s pioneering work includes developing advanced in vivo imaging techniques and genetic tools tailored for analyzing cellulose synthase trafficking. This proposal employs interdisciplinary approaches—quantitative proteomics, live-cell imaging, genome editing, and machine learning—to investigate how various trafficking components coordinate with exocytosis and endocytosis machinery to maintain steady CSC levels at the plasma membrane in a microtubule-dependent manner. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.