C <sub> 3 </ Sub> Photosynthesis In Plant Metabolic Network Dynamic Systems Biology Analysis

As a new emerging cross discipline with systems,information and life science, systems biology,based on systems theory,makes a point of integrating approach to study and quantitative analysis of biological systems behavior,which is the result of extensive interactions with their components.Systems biology promotes us to understand life more overall and deeply by simplifying and quantitating biological knowledges.The research of cell metabolic network is a very active emerging domain of systems biology.It needs not only many efficient data mining methods and making full use of the different distribution and system data,but also deep understanding of gene regulation mechanism.It's the foundation of systems biology to construct a reasonable mathematical model.In the present work,we applied stoichiometric approaches,flux balance analysis and related dynamic flux balance analysis,to explore the system dynamics characteristics of photosynthetic metabolism under drought stress or high CO₂ concentration conditions.Photosynthetic metabolism in the chloroplasts of C₃ plants was simplified into energy metabolism and carbon fixtion.The simulation is the key, and the data in model is from information of biology function,and results of modeling are presented by visualization.The main contents of this thesis are as follows:1) Simplification and reconstruction of photosynthetic metabolism in the chloroplasts of C₃ plants.If we will comprehend the changing process of cell metabolism,we have to measure all kinds of metabolites in a cell.According to the information of change,complex metabolic networks can be constructed.However, due to the limitation of measure technology,we still are not able to obtain the data of all big melaculars in biology organism.The variables describing biochemical reactions will drop a lot by simplification,which results in shortening computational time.2) Modeling the photosynthetic metabolism again by approach of dynamic flux balance analysis on the base of optimal control theory.This approach has more advantage on the description of dynamic characteristics and nonlinear essence of metabolic networks than flux balance analysis.We applied nonlinear finite element method and Legendre orthogonal polynomials to solve the approximate optimal solution in nonlinear system.3) Study on the system dynamics characteristics of photosynthetic metabolism in the chloroplasts of C₃ plants.In nature,there is no constant environment and few conditions achieving the highest effecience photosynthesis.We regarded the minimal redistribution of metabolic flux to detect the dynamic behaviour of photosynthesis under drought stress and at high CO₂ concentration perturbation.4) To make the model more logical and accurate,we added other constraints of equation and inequation when we simulated the photosynthetic metabolism by M-DFBA.The modeling results accorded with expriements and shew the dynamic process of redistribution in photosynthetic network in the face of environment stress. These will also be contributive to explore the optimal objective and potential mechanism of complex metabolic systems with external perturbation.5) We measured the correlation of mutual dependence between the velocities of photosynthetic pathways by mutual information in order to better understand the complex dynsmic system traits of the photosynthetic metabolism.We deduced that the network of far from equilibrium continuously regulated metabolic fluxes and overlapped the uncertain distribution state of system due to environment factors,and then presented a kind of commonness,which means the whole order.This cooperation function reflected the exquisite regulation and closer cooperation of interior metabolic pathways under disturbance.6) On the basis of construction and simulation of photosynthetic metabolism in the chloroplasts of C₃ plants,we validated the previous model by the wheat data,an example of C₃ plant.We obtained a deep understanding of the potential regulated mechanisms of complex systems from the similar results.The modeling results in wheat illuminate the feasibility of simplifying metabolic network,and validated reliability and stability of the previous C₃ model.By mechanism analysis of photosynthesis response to environment perturbation in wheat,we enhanced the progress in decreasing photorespiration of C₃ crops and increasing photosynthetic efficiency to improve the yields.