title: Modeling the diversion of primary carbon flux into secondary metabolism under variable nitrate and light/dark conditions.
abstract: In plants, the partitioning of carbon resources between growth and defense is detrimental for their development. From a metabolic viewpoint, growth is mainly related to primary metabolism including protein, amino acid and lipid synthesis, whereas defense is based notably on the biosynthesis of a myriad of secondary metabolites. Environmental factors, such as nitrate fertilization, impact the partitioning of carbon resources between growth and defense. Indeed, experimental data showed that a shortage in the nitrate fertilization resulted in a reduction of the plant growth, whereas some secondary metabolites involved in plant defense, such as phenolic compounds, accumulated. Interestingly, sucrose, a key molecule involved in the transport and partitioning of carbon resources, appeared to be under homeostatic control. Based on the inflow/outflow properties of sucrose homeostatic regulation we propose a global model on how the diversion of the primary carbon flux into the secondary phenolic pathways occurs at low nitrate concentrations. The model can account for the accumulation of starch during the light phase and the sucrose remobilization by starch degradation during the night. Day-length sensing mechanisms for variable light-dark regimes are discussed, showing that growth is proportional to the length of the light phase. The model can describe the complete starch consumption during the night for plants adapted to a certain light/dark regime when grown on sufficient nitrate and can account for an increased accumulation of starch observed under nitrate limitation.
authors.affiliation: INRA UMR 1121, Agronomie & Environnement Nancy-Colmar, TSA 40602, 54518 Vandoeuvre Cedex, France; Université de Lorraine UMR 1121, Agronomie & Environnement Nancy-Colmar, TSA 40602, 54518 Vandoeuvre Cedex, France. Electronic address: romain.larbat@univ-lorraine.fr.
authors.forename: Romain
authors.initials: R
authors.lastname: Larbat
authors.affiliation: INRA UMR 1121, Agronomie & Environnement Nancy-Colmar, TSA 40602, 54518 Vandoeuvre Cedex, France; Université de Lorraine UMR 1121, Agronomie & Environnement Nancy-Colmar, TSA 40602, 54518 Vandoeuvre Cedex, France.
authors.forename: Christophe
authors.initials: C
authors.lastname: Robin
authors.affiliation: Centre for Organelle Research, University of Stavanger, Stavanger Innovation Park, Måltidets Hus, 4021 Stavanger, Norway.
authors.forename: Cathrine
authors.initials: C
authors.lastname: Lillo
authors.affiliation: Department of Computer Science and Electrical Engineering, University of Stavanger, 4036 Stavanger, Norway.
authors.forename: Tormod
authors.initials: T
authors.lastname: Drengstig
authors.affiliation: Centre for Organelle Research, University of Stavanger, Stavanger Innovation Park, Måltidets Hus, 4021 Stavanger, Norway. Electronic address: peter.ruoff@uis.no.
authors.forename: Peter
authors.initials: P
authors.lastname: Ruoff
mesh_terms: D057486:Carbon Cycle / Q000187:drug effects / Q000528:radiation effects*; D003624:Darkness; D006706:Homeostasis / Q000187:drug effects / Q000528:radiation effects; D007700:Kinetics; D008027:Light; D008954:Models, Biological; D009566:Nitrates / Q000494:pharmacology; D017440:Photoperiod; D064210:Secondary Metabolism / Q000187:drug effects / Q000528:radiation effects*; D013213:Starch / Q000378:metabolism; D013395:Sucrose / Q000378:metabolism
chemical_list: D009566:Nitrates; D013395:Sucrose; D013213:Starch
keywords: Day-length measurement; Integral control; Negative feedback; Nitrate availability; Phenolic pathway; Starch; Sucrose homeostasis