title: Rhizosphere indole-3-acetic acid as a mediator in the Sorghum bicolor-phenanthrene-Sinorhizobium meliloti interactions.
abstract: We studied a model system consisting of Sorghum bicolor, phenanthrene, and an auxin-producing polycyclic aromatic hydrocarbon-degrading Sinorhizobium meliloti strain to clarify whether rhizosphere indole-3-acetic acid (IAA) takes part in the plant-pollutant-bacteria interactions. Phenanthrene and S. meliloti treatments of sorghum contributed to a decrease in the rhizosphere IAA concentration and to phytohormone accumulation, respectively. Regression analysis showed significant correlations between alteration in root-zone IAA content and alterations in the root-surface area, exudation, and rhizosphere effects for culturable heterotrophic bacteria, the S. meliloti strain, and other phenanthrene degraders. According to the data obtained, phenanthrene degraders get an advantage over nondegradative rhizobacteria from IAA for rhizosphere colonization. An IAA-dependent increase in the root-surface area leads to improved sorghum growth under pollutant stress. The carbon flux from the roots is corrected by the auxin because of its influence on the exuding-surface area and on the intensity of secretion by the root cells. On the other hand, the rhizosphere IAA pool may be plant-regulated by means of alteration in carboxylate exudation and its influence on bacterial auxin production. A scenario for the IAA-mediated S. bicolor-phenanthrene-S. meliloti interactions is proposed.
authors: Institute of Biochemistry and Physiology of Plants and Microorganisms, Russian Academy of Sciences, 13 Prospekt Entuziastov, Saratov 410049, Russia. sngolubev@rambler.ru
authors: Sergey N
authors: SN
authors: Golubev
authors: Anna Yu
authors: AY
authors: Muratova
authors: Lutz
authors: L
authors: Wittenmayer
authors: Anastasia D
authors: AD
authors: Bondarenkova
authors: Frank
authors: F
authors: Hirche
authors: Larisa Yu
authors: LY
authors: Matora
authors: Wolfgang
authors: W
authors: Merbach
authors: Olga V
authors: OV
authors: Turkovskaya
mesh_terms: D057486:Carbon Cycle; D002264:Carboxylic Acids / Q000378:metabolism; D007210:Indoleacetic Acids / Q000378:metabolism*; D008954:Models, Biological; D010616:Phenanthrenes / Q000378:metabolism / Q000494:pharmacology*; D010937:Plant Growth Regulators / Q000378:metabolism; D018517:Plant Roots / Q000187:drug effects / Q000254:growth & development* / Q000382:microbiology; D012044:Regression Analysis; D058441:Rhizosphere; D016962:Sinorhizobium meliloti / Q000378:metabolism*; D012989:Soil Pollutants / Q000378:metabolism / Q000494:pharmacology*; D045868:Sorghum / Q000187:drug effects / Q000254:growth & development* / Q000382:microbiology; D013312:Stress, Physiological
chemical_list: D002264:Carboxylic Acids; D007210:Indoleacetic Acids; D010616:Phenanthrenes; D010937:Plant Growth Regulators; D012989:Soil Pollutants; C031181:phenanthrene