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Housh AB, Powell G, Scott S, Anstaett A, Gerheart A, Benoit M, Waller S, Powell A, Guthrie JM, Higgins B, Wilder SL, Schueller MJ, Ferrieri RA. Functional mutants of Azospirillum brasilense elicit beneficial physiological and metabolic responses in Zea mays contributing to increased host iron assimilation. ISME J 2021; 15:1505-1522. [PMID: 33408368 PMCID: PMC8115672 DOI: 10.1038/s41396-020-00866-x] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/18/2020] [Revised: 10/28/2020] [Accepted: 12/03/2020] [Indexed: 01/29/2023]
Abstract
Iron (Fe), an essential element for plant growth, is abundant in soil but with low bioavailability. Thus, plants developed specialized mechanisms to sequester the element. Beneficial microbes have recently become a favored method to promote plant growth through increased uptake of essential micronutrients, like Fe, yet little is known of their mechanisms of action. Functional mutants of the epiphytic bacterium Azospirillum brasilense, a prolific grass-root colonizer, were used to examine mechanisms for promoting iron uptake in Zea mays. Mutants included HM053, FP10, and ipdC, which have varying capacities for biological nitrogen fixation and production of the plant hormone auxin. Using radioactive iron-59 tracing and inductively coupled plasma mass spectrometry, we documented significant differences in host uptake of Fe2+/3+ correlating with mutant biological function. Radioactive carbon-11, administered to plants as 11CO2, provided insights into shifts in host usage of 'new' carbon resources in the presence of these beneficial microbes. Of the mutants examined, HM053 exhibited the greatest influence on host Fe uptake with increased plant allocation of 11C-resources to roots where they were transformed and exuded as 11C-acidic substrates to aid in Fe-chelation, and increased C-11 partitioning into citric acid, nicotianamine and histidine to aid in the in situ translocation of Fe once assimilated.
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Affiliation(s)
- A B Housh
- Missouri Research Reactor Center, University of Missouri, Columbia, MO, 65211, USA
- Chemistry Department, University of Missouri, Columbia, MO, 65211, USA
| | - G Powell
- Missouri Research Reactor Center, University of Missouri, Columbia, MO, 65211, USA
- Department of Biochemistry, University of Missouri, Columbia, MO, 65211, USA
| | - S Scott
- Missouri Research Reactor Center, University of Missouri, Columbia, MO, 65211, USA
- Department of Biochemistry, University of Missouri, Columbia, MO, 65211, USA
| | - A Anstaett
- Missouri Research Reactor Center, University of Missouri, Columbia, MO, 65211, USA
- Department of Chemical Engineering, University of Missouri, Columbia, MO, 65211, USA
- Burns & McDonnell, Inc. 425 S, Woods Mill Rd., Chesterfield, MO, USA, 63017
| | - A Gerheart
- Missouri Research Reactor Center, University of Missouri, Columbia, MO, 65211, USA
- Chemistry Department, University of Missouri, Columbia, MO, 65211, USA
- Idaho State Police 5255 S. 5th Ave, Pocatello, ID, 83204, USA
| | - M Benoit
- Missouri Research Reactor Center, University of Missouri, Columbia, MO, 65211, USA
- Division of Plant Sciences, University of Missouri, Columbia, MO, 65211, USA
| | - S Waller
- Missouri Research Reactor Center, University of Missouri, Columbia, MO, 65211, USA
- School of Natural Resources, University of Missouri, Columbia, MO, 65211, USA
| | - A Powell
- Missouri Research Reactor Center, University of Missouri, Columbia, MO, 65211, USA
- School of Natural Resources, University of Missouri, Columbia, MO, 65211, USA
| | - J M Guthrie
- Missouri Research Reactor Center, University of Missouri, Columbia, MO, 65211, USA
| | - B Higgins
- Missouri Research Reactor Center, University of Missouri, Columbia, MO, 65211, USA
| | - S L Wilder
- Missouri Research Reactor Center, University of Missouri, Columbia, MO, 65211, USA
| | - M J Schueller
- Missouri Research Reactor Center, University of Missouri, Columbia, MO, 65211, USA
- Chemistry Department, University of Missouri, Columbia, MO, 65211, USA
| | - R A Ferrieri
- Missouri Research Reactor Center, University of Missouri, Columbia, MO, 65211, USA.
- Chemistry Department, University of Missouri, Columbia, MO, 65211, USA.
- Division of Plant Sciences, University of Missouri, Columbia, MO, 65211, USA.
- Interdisciplinary Plant Group, University of Missouri, Columbia, MO, 65211, USA.
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