CAREER: Elucidating the hormonal regulation of cellulose synthase complexes by post-translational phosphorylation

This project seeks to understand how plants control the synthesis of cellulose, a critically important polysaccharide that governs plant growth and development. Cellulose is an important component of food, fiber, textiles, and fuel for human and forage animals. While many of the enzymes that participate in cellulose synthesis in land plants have been identified, it is still unclear how plants make the decision to produce more or less cellulose. The Wallace lab will use advanced genetic, biochemical, and cell biological techniques to elucidate how cellulose biosynthesis is controlled during normal plant development and in response to changing environmental conditions, such as heat, drought, salt stress, and limiting nutrients. This information will be utilized to engineer plants with increased cellulose contents that could be used as biomass feedstocks for the synthesis of sustainable value-added products or as more efficient feedstocks for forage animals. By understanding how cellulose biosynthesis is controlled, the investigator also expects to provide a foundation for understanding how this fundamental feature of plant cell biology is linked to plant growth and development. Additionally, this project will support the research training of graduate, undergraduate, and high school students from diverse and under-represented backgrounds. This project will also support the course development of a quantitative mass spectrometry module for undergraduate students as well as public outreach through local agricultural events and web-based videos. The long-term goal is to understand how plant cellulose biosynthesis is controlled by post-translational phosphorylation, and to utilize this knowledge to increase cellulose output under changing environmental conditions. The central hypothesis guiding this research effort is that CESA (Cellulose synthase A) subunits and other CSC (Cellulose Synthase Complex) components are phosphorylated by protein kinases involved in the brassinosteroid signaling cascade, and these phosphorylation events regulate CSC velocity or subcellular localization. Specific Aim 1 employs biochemical and genetic methods to identify brassinosteroid-regulated protein kinases that phosphorylate and regulate components of the CSC and to understand how these regulatory events control plant growth and development. Specific Aim 2 utilizes advanced quantitative proteomic methods to investigate how changing environmental conditions lead to alterations in CSC phosphorylation. Specific Aim 3 focuses on determining how phosphorylation of CESA subunits influences the in vitro enzymatic activity of cellulose biosynthesis. The unifying goal of this work is to develop a holistic understanding of how post-translational phosphorylation regulates that activity of the CSC both in vitro and in vivo. 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.