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Environmental Transformations and Interactions

A New, Nondestructive RhizoMAP Platform Allows for Metabolic Imaging of Rhizosphere

Researchers developed a new platform called RhizoMAP that allows them to spatially and temporally map active exuded components in the rhizosphere. 

Spatial distributions of exemplary rhizosphere organics throughout the root length and associated rhizosphere

Through a new platform called RhizoMAP, researchers are now applying state-of-the-art chemical derivatization alongside other methodologies to spatially and temporally map active exuded components using mass spectrometry imaging. (Image courtesy of the Environmental Molecular Sciences Laboratory)

The Science 

Imaging the rhizosphere, which is the zone of soil under the direct influence of plant roots, typically is a destructive processs. Previously, researchers were unable to nondestructively image the complex dynamics between a plant’s root system and soil microenvironments. Through the development of the RhizoMAP platform, however, researchers are now applying state-of-the-art chemical derivatization alongside other methodologies with passive imprinting to spatially and temporally map active exuded components using mass spectrometry imaging (MSI). These components include primary and secondary metabolites from plant roots and various microbial molecules. This new platform enables researchers to trace and visualize complex metabolomic processes in the rhizosphere in the presence of the microbial community and in changing environments like drought conditions. 

The Impact 

Being able to spatiotemporally map metabolites within the rhizosphere opens up a new realm of possibilities for the scientific community. Using RhizoMap coupled with Fourier-transform ion cyclotron resonance mass spectrometry capabilities, users at the Environmental Molecular Sciences Laboratory, a Department of Energy (DOE) Office of Science user facility, are now able to track key metabolites at root–soil–microbe interfaces. Confident annotation of a wide range of molecules, including the identification of exudate profiles, will provide information on rhizosphere processes where plants secrete a variety of exudates based on their growth cycles and environmental stimuli in the soil. The data from RhizoMap can help to develop mechanistic ecosystem-level models to improve the understanding of molecular and microscale processes that control organic carbon stability and transformation in soil. 

Summary 

RhizoMAP is a capability that provides nondestructive, untargeted, broad, and sensitive metabolite imaging of the root-associated molecules, exudates, and soil organic matter throughout the rhizosphere in a native soil environment. Now, researchers can capture molecular distributions and gradients of key metabolites up to and beyond a 20 cm deep rhizosphere. While RhizoMAP was originally used to image the rhizosphere of poplar (Populus trichocarpa) grown in rhizoboxes as a proof of concept, researchers can use any soil source and study any plant system to discover novel processes in the rhizosphere. A comprehensive view of the fine distributions of metabolites within the root–soil interface has remained a significant challenge, but RhizoMAP is poised to address this. 

Contacts 

Amir Ahkami,  EMSL | Pacific Northwest National Laboratory, amir.ahkami@pnnl.gov 

Dušan Veličković,  EMSL | Pacific Northwest National Laboratory, dusan.velickovic@pnnl.gov 

Kevin Zemaitis, EMSL | Pacific Northwest National Laboratory, kevin.zemaitis@pnnl.gov 

Funding 

This research was performed on a project award from the Environmental Molecular Sciences Laboratory, a DOE Office of Science User Facility sponsored by the Biological and Environmental Research program. 

Publication 

D. Veličković, et al. “RhizoMAP: a comprehensive, nondestructive, and sensitive platform for metabolic imaging of the rhizosphere.” Plant Methods 20, 117 (2024). [DOI: 10.1186/s13007-024-01249-5]