Magnetic resonance imaging (MRI) is a flexible technique widely used in biomedical research; however, utilizing it to analyze plant metabolism in living organisms has proven to be difficult. A team of researchers led by Dr. L. Borisjuk from the IPK Leibniz Institute, along with Prof. P.M. Jakob from Würzburg University, has developed a method known as chemical exchange saturation transfer (CEST) specifically for MRI in plants. This innovative approach allows for noninvasive examination of sugar and amino acid metabolism within complex sink organs—including seeds, fruits, taproots, and tubers—of significant crops such as maize, barley, pea, potato, sugar beet, and sugarcane. Their findings have recently been published in the journal Science Advances.
The “omics” technologies—genomics, transcriptomics, proteomics, and metabolomics—are leading the way in modern plant science and systems biology. Unlike the comparatively “static” genome, the metabolome is dynamic and influenced by various spatial and temporal factors. In the biomedical realm, one of the most influential technologies for in vivo metabolic diagnostics and functional studies is nuclear magnetic resonance (NMR) imaging or MRI. However, similar approaches in plant science have not been fully explored until now.
An interdisciplinary team known as “Assimilate Allocation and NMR” at the IPK is focused on harnessing the potential of NMR imaging in the field of plant science. Thanks to funding from the European Regional Development Fund (ERDF) and the Investment Bank of Saxony-Anhalt, they have successfully established a new NMR platform that forms a crucial part of their research.
Traditional H NMR imaging in biological tissues primarily detects signals from water or lipid protons. Since the concentration of metabolite protons is significantly lower—by at least three orders of magnitude—detecting these metabolites in vivo necessitates the effective suppression of water signals.
Chemical exchange saturation transfer (CEST), a technique already utilized in biomedical applications, may present a solution. With CEST, magnetization is transferred from various molecules to water molecules, allowing the saturation effects initially affecting the target species to be perceived in the water signal instead. “This method enables us to identify a range of metabolites based on their proton exchange capabilities with water, thereby enhancing MRI contrast,” explains Simon Mayer, the lead author of the study and a researcher at IPK Leibniz Institute. “Due to its high sensitivity in signal detection and resilience to magnetic field variations, CEST can analyze heterogeneous botanical samples that traditional magnetic resonance spectroscopy cannot reach.”
The results are promising. “Our research indicates that CEST is an effective MRI technique that supports in vivo metabolic analysis in plants, facilitating microscopic resolution and dynamic evaluation of sugar and amino acid distribution despite the complexity of the samples’ magnetic environment. Its applicability across different crops highlights that CEST is a versatile method that can visually track metabolites without needing prior labeling or sample alteration,” notes Dr. Ljudmilla Borisjuk, the head of the IPK’s “Assimilate Allocation and NMR” research group.
The research team was able to observe metabolite dynamics in growing seeds, something impossible with conventional methods. There is a strong demand from breeders for insights into the spatiotemporal behavior of sugars and amino acids in sink organs, as their distribution affects mass transport and metabolism, ultimately influencing crop improvement.
The introduction of CEST unlocks new possibilities for monitoring changing metabolite landscapes in living plants, which is critical for a better understanding of trait development while also aiding breeding research through in vivo analysis of metabolic responses to genetic modifications and developmental changes.
“Visualizing metabolite dynamics in live plants is a sought-after capability that connects structural and metabolic interactions in response to variable environments. The integration of CEST, which showcases both internal tissue structures and metabolite dynamics without the use of tracers—all through the singular technology of MRI—marks an important milestone in this pursuit.”
