NC1142: Regulation of Photosynthetic Processes (Rev. NC-142)
Statement of Issues and Justification
Photosynthesis is the primary determinant of crop productivity. It is the single process on earth that converts sunlight into biomass, sequesters atmospheric CO2 into carbohydrates, and liberates O2. Photosynthesis and the resulting yields of food and fiber products are dramatically limited by environmental constraints in agricultural contexts as reflected by the fact that average yields are typically much less than the maximal yields possible when efficiency and sustainability concerns are relaxed.Whereas agricultural productivity continues to increase slowly, the rate of increase has declined steadily since the 1960's, and it may soon plateau (Mann, 1998). Thus, there is increasing concern that future increases, essential to enhance the competitiveness of U.S. agriculture and to fulfill global demands for food and fiber, will be dependent on the development of new approaches to increase the capacity of crop plants to produce the nutrients that support the growth of harvested plant parts. New approaches will also be required to enhance efficiency and to improve agricultural sustainability. To achieve these goals, it will be essential to gain fundamental knowledge of the underlying metabolic components that control assimilate production and utilization, and hence plant growth and development. This knowledge must include an understanding of the regulation of important photosynthetic enzymes and how environmental and developmental signals affecting photosynthetic processes are perceived at the molecular and gene levels. Such knowledge will provide new opportunities for crop improvement using the techniques of both molecular genetics and classical breeding.
The proposed multistate research project brings together some of the most outstanding, productive photosynthesis investigators in the country in an integrated effort to broaden our understanding of critically important areas of photosynthesis research. We propose a synergistic, cooperative research program that concentrates on four areas of photosynthetic regulation:
1. Photochemistry and the biogenesis of the photosynthetic apparatus. The purpose of this research is to understand the structure and function of the light harvesting and electron transfer components of the thylakoid membrane, with emphasis on Photosystem I and the mechanisms that control the stoichiometry between Photosystems I and II. Anterograde and retrograde pathways involved in coordinating the expression of nuclear and chloroplast genes for photosynthetic proteins will be studied, and novel photosynthetic proteins will be identified. The collaborating units include IA-AES, NE-AES and OR-AES (3 institutions, 4 research labs).
2. Photosynthetic capture and photorespiratory release of CO2. The goal of this research is to determine and modify the biochemical and regulatory factors that impact photosynthetic capture and photorespiratory release of CO2. Particular emphasis will be placed on understanding protein-protein interactions and post-translational modifications of key photosynthetic enzymes involved in primary and secondary CO2 assimilation, as well as the mechanisms that control carbon flux through primary and secondary metabolic pathways. The collaborating units include IL-ARS, KY-AES, MO-AES, NE-AES, and NV-AES (5 institutions, 6 research labs).
3. Mechanisms regulating photosynthate partitioning. The objective of this research is to gain insight into the mechanisms that regulate photosynthate partitioning into pathways of biosynthesis and use of sucrose, starch, and sugar alcohols. These studies will examine interactions between compartments of the cell, between plant parts, and the partitioning of carbohydrates between transport, storage, and stress-protective functions. The collaborating units include FL-AES, IA-AES, IL-AES, MI-AES, MN-AES, NC-AES, NE-AES, PA-AES, SC-AES, WA-AES, WI-AES (11 institutions, 13 research labs).
4. Developmental and environmental limitations to photosynthesis. The aim of this research is to analyze the limitations and environmental factors that influence photosynthetic productivity at the whole plant and canopy levels. Particular emphasis will be placed on abiotic stresses (temperature, water, and salinity), nitrogen use, and global atmospheric change. This work will integrate understanding developed here and under objectives 1 through 3 to optimize photosynthetic production and yield under current and future environmental conditions. The collaborating units include Guam-AES, IA-AES, IL-AES, KS-AES, MI-AES, MS-ARS, NE-AES, NV-AES, OR-AES, WA-AES (10 institutions, 14 research labs).
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