title: Auxin secretion by Bacillus amyloliquefaciens FZB42 both stimulates root exudation and limits phosphorus uptake in Triticum aestivium.
abstract: BACKGROUND
  The use of auxin-producing rhizosphere bacteria as agricultural products promises increased root production and therefore greater phosphate (Pi) uptake. Whilst such bacteria promote root production in vitro, the nature of the bacteria-plant interaction in live soil, particularly concerning any effects on nutrient uptake, are not known. This study uses Bacillus amyloliquefaciens FZB42, an auxin-producing rhizobacterium, as a dressing on Triticum aestivium seeds. It then examines the effects on root production, Pi uptake, Pi-related gene expression and organic carbon (C) exudation.
  
  
  RESULTS
  Seed treatment with B. amyloliquefaciens FZB42 increased root production at low environmental Pi concentrations, but significantly repressed root Pi uptake. This coincided with an auxin-mediated reduction in expression of the Pi transporters TaPHT1.8 and TaPHT1.10. Applied exogenous auxin also triggered an increase in root C exudation. At high external Pi concentrations, root production was promoted by B. amyloliquefaciens FZB42, but Pi uptake was unaffected.
  
  
  CONCLUSIONS
  We conclude that, alongside promoting root production, auxin biosynthesis by B. amyloliquefaciens FZB42 both re-models Pi transporter expression and elevates organic C exudation. This shows the potential importance of rhizobacterial-derived auxin following colonisation of root surfaces, and the nature of this bacteria-plant interaction in soil.
authors.affiliation: School of Environment, Natural Resources and Geography, College of Natural Sciences, Bangor University, Bangor, Gwynedd LL57 2DG, UK. p.j.talboys@bangor.ac.uk.
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Talboys
authors.forename: Darren W
authors.initials: DW
authors.lastname: Owen
authors.forename: John R
authors.initials: JR
authors.lastname: Healey
authors.forename: Paul J A
authors.initials: PJ
authors.lastname: Withers
authors.forename: David L
authors.initials: DL
authors.lastname: Jones
mesh_terms: D001407:Bacillus / Q000378:metabolism* / Q000502:physiology; D007210:Indoleacetic Acids / Q000378:metabolism*; D010758:Phosphorus / Q000378:metabolism*; D018517:Plant Roots / Q000378:metabolism* / Q000382:microbiology; D014908:Triticum / Q000378:metabolism* / Q000382:microbiology
chemical_list: D007210:Indoleacetic Acids; D010758:Phosphorus