title: Elucidating rice cell metabolism under flooding and drought stresses using flux-based modeling and analysis.
abstract: Rice (Oryza sativa) is one of the major food crops in world agriculture, especially in Asia. However, the possibility of subsequent occurrence of flood and drought is a major constraint to its production. Thus, the unique behavior of rice toward flooding and drought stresses has required special attention to understand its metabolic adaptations. However, despite several decades of research investigations, the cellular metabolism of rice remains largely unclear. In this study, in order to elucidate the physiological characteristics in response to such abiotic stresses, we reconstructed what is to our knowledge the first metabolic/regulatory network model of rice, representing two tissue types: germinating seeds and photorespiring leaves. The phenotypic behavior and metabolic states simulated by the model are highly consistent with our suspension culture experiments as well as previous reports. The in silico simulation results of seed-derived rice cells indicated (1) the characteristic metabolic utilization of glycolysis and ethanolic fermentation based on oxygen availability and (2) the efficient sucrose breakdown through sucrose synthase instead of invertase. Similarly, flux analysis on photorespiring leaf cells elucidated the crucial role of plastid-cytosol and mitochondrion-cytosol malate transporters in recycling the ammonia liberated during photorespiration and in exporting the excess redox cofactors, respectively. The model simulations also unraveled the essential role of mitochondrial respiration during drought stress. In the future, the combination of experimental and in silico analyses can serve as a promising approach to understand the complex metabolism of rice and potentially help in identifying engineering targets for improving its productivity as well as enabling stress tolerance.
authors.affiliation: Department of Chemical and Biomolecular Engineering, National University of Singapore, Singapore 117576.
authors.forename: Meiyappan
authors.initials: M
authors.lastname: Lakshmanan
authors.forename: Zhaoyang
authors.initials: Z
authors.lastname: Zhang
authors.forename: Bijayalaxmi
authors.initials: B
authors.lastname: Mohanty
authors.forename: Jun-Young
authors.initials: JY
authors.lastname: Kwon
authors.forename: Hong-Yeol
authors.initials: HY
authors.lastname: Choi
authors.forename: Hyung-Jin
authors.initials: HJ
authors.lastname: Nam
authors.forename: Dong-Il
authors.initials: DI
authors.lastname: Kim
authors.forename: Dong-Yup
authors.initials: DY
authors.lastname: Lee
mesh_terms: D000596:Amino Acids / Q000096:biosynthesis; D002952:Citric Acid Cycle; D003198:Computer Simulation; D003600:Cytosol / Q000378:metabolism; D055864:Droughts; D055868:Floods; D018525:Germination; D006019:Glycolysis; D053858:Metabolic Networks and Pathways; D008954:Models, Biological; D012275:Oryza / Q000378:metabolism / Q000502:physiology*; D010085:Oxidative Phosphorylation; D010100:Oxygen / Q000378:metabolism; D059828:Plant Cells / Q000378:metabolism*; D018515:Plant Leaves / Q000166:cytology / Q000502:physiology; D012639:Seeds / Q000502:physiology; D013312:Stress, Physiological
chemical_list: D000596:Amino Acids; D010100:Oxygen