A Theoretical Approach to Guiding Biotechnological Improvement of Crop Photosynthetic Efficiency
Zhu, Xinguang
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https://hdl.handle.net/2142/87047
Description
Title
A Theoretical Approach to Guiding Biotechnological Improvement of Crop Photosynthetic Efficiency
Author(s)
Zhu, Xinguang
Issue Date
2004
Doctoral Committee Chair(s)
Long, Stephen P.
Department of Study
Plant Biology
Discipline
Plant Biology
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Biology, Cell
Language
eng
Abstract
This thesis aims to use computational modeling approaches to advance identifying targets for higher photosynthetic efficiency. Two approaches have been identified that can substantially increase daily canopy photosynthetic CO2 uptake rate (Ac). Replacement of current C3 crop Rubisco with foreign Rubisco with higher catalytic rates was shown to increase Ac by up to 31%. Increased recovery from photoprotection to increase efficiency of photosynthesis of leaves in the shade, could increase Ac by ca. 15%, and by more at lower temperatures. In order to expedite the identification of targets for genetic manipulations for higher net photosynthetic CO 2 uptake rates, a dynamic model of photosynthesis, e-Photosynthesis was developed using a 'divide and conquer' strategy, i.e. dividing the photosynthesis process into three functional units, developing independent models for each, and finally combining them altogether to assemble the complete model of photosynthesis. The model of carbon metabolism incorporates the photorespiratory carbon oxidation pathway (PCOP) in addition to the Calvin cycle, starch synthesis, and triose phosphate export. Simulations using this model revealed that enzymes in PCOP are in excess for maintaining the flux to PCOP under normal atmospheric condition; this excess of enzyme activities may be an insurance against environmental conditions that promote photorespiration. The model of primary events around PSII includes all energy and electron transfer in and around photosystem II. This model successfully simulates the fluorescence induction kinetics. Simulations using this model provide theoretical interpretation of the origins of the different phases of fluorescence induction curve and illustrate the effects of changes in kinetic and structural properties in the photosystem on the fluorescence induction curve. The model of electron transfer extends the model of primary events around PSII to include excitation energy and electron transfer processes around PSI, ion transfer, ATP and NADPH production. Simulations using the model of electron transfer predicted that a steady-state electrical potential across thylakoid membrane exists under light. e-Photosynthesis model realistically predicted photosynthetic kinetics upon changes in photon flux density and CO2 concentrations. e-Photosynthesis provides a numerical platform for identifying targets for higher radiation energy conversion efficiency and to test hypotheses about photosynthetic kinetics.
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