title: High CO2 triggers preferential root growth of Arabidopsis thaliana via two distinct systems under low pH and low N stresses.
abstract: Biomass allocation between shoots and roots is an important strategy used by plants to optimize growth in various environments. Root to shoot mass ratios typically increase in response to high CO2, a trend particularly evident under abiotic stress. We investigated this preferential root growth (PRG) in Arabidopsis thaliana plants cultivated under low pH/high CO2 or low nitrogen (N)/high CO2 conditions. Previous studies have suggested that changes in plant hormone, carbon (C) and N status may be related to PRG. We therefore examined the mechanisms underlying PRG by genetically modifying cytokinin (CK) levels, C and N status, and sugar signaling, performing sugar application experiments and determining primary metabolites, plant hormones and expression of related genes. Both low pH/high CO2 and low N/high CO2 stresses induced increases in lateral root (LR) number and led to high C/N ratios; however, under low pH/high CO2 conditions, large quantities of C were accumulated, whereas under low N/high CO2 conditions, N was severely depleted. Analyses of a CK-deficient mutant and a starchless mutant, in conjunction with sugar application experiments, revealed that these stresses induce PRG via different mechanisms. Metabolite and hormone profile analysis indicated that under low pH/high CO2 conditions, excess C accumulation may enhance LR number through the dual actions of increased auxin and decreased CKs.
authors.affiliation: Department of Biological Sciences, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033 Japan.
authors.forename: Takushi
authors.initials: T
authors.lastname: Hachiya
authors.forename: Daisuke
authors.initials: D
authors.lastname: Sugiura
authors.forename: Mikiko
authors.initials: M
authors.lastname: Kojima
authors.forename: Shigeru
authors.initials: S
authors.lastname: Sato
authors.forename: Shuichi
authors.initials: S
authors.lastname: Yanagisawa
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Sakakibara
authors.forename: Ichiro
authors.initials: I
authors.lastname: Terashima
authors.forename: Ko
authors.initials: K
authors.lastname: Noguchi
mesh_terms: D017360:Arabidopsis / Q000187:drug effects / Q000254:growth & development / Q000502:physiology*; D018533:Biomass; D002241:Carbohydrates / Q000032:analysis; D002245:Carbon Dioxide / Q000378:metabolism / Q000494:pharmacology*; D003583:Cytokinins / Q000032:analysis / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007210:Indoleacetic Acids / Q000032:analysis / Q000378:metabolism; D009584:Nitrogen / Q000172:deficiency* / Q000378:metabolism; D010937:Plant Growth Regulators / Q000032:analysis / Q000378:metabolism*; D018517:Plant Roots / Q000187:drug effects / Q000254:growth & development / Q000502:physiology; D018520:Plant Shoots / Q000187:drug effects / Q000254:growth & development / Q000502:physiology; D036226:Seedlings / Q000187:drug effects / Q000254:growth & development / Q000502:physiology; D015398:Signal Transduction; D012987:Soil; D013312:Stress, Physiological
chemical_list: D002241:Carbohydrates; D003583:Cytokinins; D007210:Indoleacetic Acids; D010937:Plant Growth Regulators; D012987:Soil; D002245:Carbon Dioxide; D009584:Nitrogen
keywords: Auxin; Cytokinin; High CO2; Low nitrogen; Low pH; Root to shoot ratio