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SUMMARY The establishment of the nitrogen‐fixing symbiosis between soybean andBradyrhizobium japonicumis a complex process. To document the changes in plant metabolism as a result of symbiosis, we utilized laser ablation electrospray ionization‐mass spectrometry (LAESI‐MS) forin situmetabolic profiling of wild‐type nodules, nodules infected with aB. japonicum nifHmutant unable to fix nitrogen, nodules doubly infected by both strains, and nodules formed on plants mutated in thestearoyl‐acyl carrier protein desaturase(sacpd‐c) gene, which were previously shown to have an altered nodule ultrastructure. The results showed that the relative abundance of fatty acids, purines, and lipids was significantly changed in response to the symbiosis. ThenifHmutant nodules had elevated levels of jasmonic acid, correlating with signs of nitrogen deprivation. Nodules resulting from the mixed inoculant displayed similar, overlapping metabolic distributions within the sectors of effective (fix+) and ineffective (nifHmutant, fix−) endosymbionts. These data are inconsistent with the notion that plant sanctioning is cell autonomous. Nodules lackingsacpd‐cdisplayed an elevation of soyasaponins and organic acids in the central necrotic regions. The present study demonstrates the utility of LAESI‐MS for high‐throughput screening of plant phenotypes. Overall, nodules disrupted in the symbiosis were elevated in metabolites related to plant defense.
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An integrated electrocatalytic nESI-MS platform for quantification of fatty acid isomers directly from untreated biofluids
Positional isomers of alkenes are frequently transparent to the mass spectrometer and it is difficult to provide convincing data to support their presence. This work focuses on the development of a new reactive nano-electrospray ionization (nESI) platform that utilizes non-inert metal electrodes ( e.g. , Ir and Ru) for rapid detection of fatty acids by mass spectrometry (MS), with concomitant localization of the CC bond to differentiate fatty acid isomers. During the electrospray process, the electrical energy (direct current voltage) is harnessed for in situ oxide formation on the electrode surface via electro-oxidation. The as-formed surface oxides are found to facilitate in situ epoxide formation at the CC bond position and the products are analyzed by MS in real-time. This phenomenon has been applied to analyze isomers of unsaturated fatty acids from complex serum samples, without pre-treatment.
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- Award ID(s):
- 1900271
- PAR ID:
- 10244158
- Date Published:
- Journal Name:
- Chemical Science
- Volume:
- 11
- Issue:
- 36
- ISSN:
- 2041-6520
- Page Range / eLocation ID:
- 9891 to 9897
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/d0sc03403g
