Magnetic Resonance Microscopy at Cellular Resolution and Localised Spectroscopy of Medicago truncatula at 22.3 Tesla

• Published in: Scientific reports Vol. 10; no. 1; p. 971
• Main Authors: van Schadewijk, Remco, Krug, Julia R., Shen, Defeng, Sankar Gupta, Karthick B. S., Vergeldt, Frank J., Bisseling, Ton, Webb, Andrew G., Van As, Henk, Velders, Aldrik H., de Groot, Huub J. M., Alia, A.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 22-01-2020; Nature Publishing Group
• Subjects: 14/63; 140/131; 59/57; 631/1647/245/1628; 631/449/2676/2678; Alfalfa; Asparagine; Betaine; Choline; Ecosystem; Flora; Food plants; Food production; Fungal flora; Humanities and Social Sciences; Magnetic fields; Magnetic Resonance Spectroscopy; Medicago truncatula; Medicago truncatula - genetics; Medicago truncatula - metabolism; Metabolism; Metabolites; Microscopy; Morphology; multidisciplinary; Nitrogen Fixation; Root nodules; Root Nodules, Plant - metabolism; Root Nodules, Plant - microbiology; Science; Science (multidisciplinary); Soil Microbiology; Spatial distribution; Spectroscopy; Spectrum analysis
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-020-57861-7

Interactions between plants and the soil’s microbial & fungal flora are crucial for the health of soil ecosystems and food production. Microbe-plant interactions are difficult to investigate
in situ
due to their intertwined relationship involving morphology and metabolism. Here, we describe an approach to overcome this challenge by elucidating morphology and the metabolic profile of
Medicago truncatula
root nodules using Magnetic Resonance (MR) Microscopy, at the highest magnetic field strength (22.3 T) currently available for imaging. A home-built solenoid RF coil with an inner diameter of 1.5 mm was used to study individual root nodules. A 3D imaging sequence with an isotropic resolution of (7 μm)
3
was able to resolve individual cells, and distinguish between cells infected with rhizobia and uninfected cells. Furthermore, we studied the metabolic profile of cells in different sections of the root nodule using localised MR spectroscopy and showed that several metabolites, including betaine, asparagine/aspartate and choline, have different concentrations across nodule zones. The metabolite spatial distribution was visualised using chemical shift imaging. Finally, we describe the technical challenges and outlook towards future
in vivo
MR microscopy of nodules and the plant root system.