Linking the depletion of rhizosphere phosphorus to the heterologous expression of a fungal phytase in Nicotiana tabacum as revealed by enzyme-labile P and solution 31P NMR spectroscopy

Courtney D. Giles*, Timothy S. George, Lawrie K. Brown, Malika Mezeli, Charles A. Shand, Alan E. Richardson, Regina Mackay, Renate Wendler, Tegan Darch, Daniel Menezes-Blackburn, Pat Cooper, Marc I. Stutter, David G. Lumsdon, Martin S.A. Blackwell, Catherine Wearing, Hao Zhang, Philip M. Haygarth

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

9 Citations (Scopus)

Abstract

Root exudation of phytase could improve the ability of plants to access organic forms of soil phosphorus (P), thereby minimizing fertilizer requirements and improving P use efficiency in agroecosystems. After 75 days growth in a high available P soil, shoot biomass and P accumulation, soil pH, and rhizosphere P depletion were investigated in Nicotiana tabacum wild-type and transgenic plant-lines expressing and exuding Aspergillus niger phytase (ex::phyA), or a null-vector control. Solution 31P NMR analysis revealed a 7% to 11% increase in orthophosphate and a comparable depletion of undefined monoester P compounds (-13 to -18%) in the rhizosphere of tobacco plants relative to the unplanted soil control. Wild-type plants had the greatest impact on the composition of rhizosphere P based on the depletion of other monoester P, polyphosphate, and phosphonate species. The depletion of phytase-labile P by ex::phyA plants was associated with decreased proportions of other monoester P, rather than myo-InsP6 as expected. Rhizosphere pH increased from 6.0 to 6.5-6.7 in transgenic plant soils, beyond the pH optimum for A. niger phyA activity (pH=5), and may explain the limited specificity of ex::phyA plants for phytate in this soil. The efficacy of single exudation traits (e.g., phytase) therefore appear to be limited in P-replete soil conditions and may be improved where soil pH matches the functional requirements of the enzyme or trait of interest.

Original languageEnglish
Pages (from-to)82-91
Number of pages10
JournalRhizosphere
Volume3
DOIs
Publication statusPublished - Jun 2017

Keywords

  • P NMR spectroscopy
  • pH
  • Phosphorus
  • Phytase
  • Phytate
  • Tobacco

ASJC Scopus subject areas

  • Agronomy and Crop Science
  • Soil Science
  • Plant Science

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