Metabolic interactions between brachypodium and pseudomonas fluorescens under controlled iron-limited conditions

Rene M. Boiteau, Lye Meng Markillie, David W. Hoyt, Dehong Hu, Rosalie K. Chu, Hugh D. Mitchell, Ljiljana Pasa-Tolic, Janet K. Jansson, Christer Jansson

Research output: Contribution to journalArticlepeer-review

13 Scopus citations

Abstract

Iron (Fe) availability has well-known effects on plant and microbial metabolism, but its effects on interspecies interactions are poorly understood. The purpose of this study was to investigate metabolite exchange between the grass Brachypodium distachyon strain Bd21 and the soil bacterium Pseudomonas fluorescens SBW25::gfp/lux (SBW25) during Fe limitation under axenic conditions. We compared the transcriptional profiles and root exudate metabolites of B. distachyon plants grown semihydroponically with and without SBW25 inoculation and Fe amendment. Liquid chromatography-mass spectrometry analysis of the hydroponic solution revealed an increase in the abundance of the phytosiderophores mugineic acid and deoxymugineic acid under Fe-limited conditions compared to Fe-replete conditions, indicating greater secretion by roots presumably to facilitate Fe uptake. In SBW25-inoculated roots, expression of genes encoding phytosiderophore biosynthesis and uptake proteins increased compared to that in sterile roots, but external phytosiderophore abundances decreased. P. fluorescens siderophores were not detected in treatments without Fe. Rather, expression of SBW25 genes encoding a porin, a transporter, and a monooxygenase was significantly upregulated in response to Fe deprivation. Collectively, these results suggest that SBW25 consumed root-exuded phytosiderophores in response to Fe deficiency, and we propose target genes that may be involved. SBW25 also altered the expression of root genes encoding defense-related enzymes and regulators, including thionin and cyanogenic glycoside production, chitinase, and peroxidase activity, and transcription factors. Our findings provide insights into the molecular bases for the stress response and metabolite exchange of interacting plants and bacteria under Fe-deficient conditions.

Original languageEnglish (US)
Article numbere00580-20
JournalmSystems
Volume6
Issue number1
DOIs
StatePublished - Feb 2021
Externally publishedYes

Bibliographical note

Funding Information:
This research was supported by the Department of Energy (DOE) Office of Biological and Environmental Research (BER) and was conducted at the Environmental Molecular Sciences Laboratory (EMSL), a DOE user facility, as a contribution of the EMSL Strategic Science Area under project 22142. R. M. Boiteau was funded by the Linus Pauling Postdoctoral Fellowship LDRD 204495 from the Pacific Northwest National Lab (PNNL) and the Simons Foundation (award 621513). PNNL is operated for the DOE by Battelle Memorial Institute under contract DE-AC05-76RLO1830.

Publisher Copyright:
© 2021 Boiteau et al.

Keywords

  • Grass
  • Iron
  • Siderophore

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