Metabolomics as an Emerging Tool for the Study of Plant-Pathogen Interactions

Abstract

Plants defend themselves from most microbial attacks via mechanisms including cell wall fortification, production of antimicrobial compounds, and generation of reactive oxygen species. Successful pathogens overcome these host defenses, as well as obtain nutrients from the host. Perturbations of plant metabolism play a central role in determining the outcome of attempted infections. Metabolomic analyses, for example between healthy, newly infected and diseased or resistant plants, have the potential to reveal perturbations to signaling or output pathways with key roles in determining the outcome of a plant-microbe interaction. However, application of this -omic and its tools in plant pathology studies is lagging relative to genomic and transcriptomic methods. Thus, it is imperative to bring the power of metabolomics to bear on the study of plant resistance/susceptibility. This review discusses metabolomics studies that link changes in primary or specialized metabolism to the defense responses of plants against bacterial, fungal, nematode, and viral pathogens. Also examined are cases where metabolomics unveils virulence mechanisms used by pathogens. Finally, how integrating metabolomics with other -omics can advance plant pathology research is discussed.

Keywords: gas-chromatography; liquid-chromatography; mass spectrometry; microbe; pathogen; plant; primary metabolites; specialized metabolites.

Figure 1

Plant metabolism. Primary metabolism (yellow) revolves around critical physiological compounds such as amino acids and sugars. Secondary metabolism (blue) utilizes central metabolites as building blocks for the biosynthesis of specialized compounds such as flavonoids, toxins, and lipids that have various functions (green), including plant growth and defense against stresses.

Figure 2

Metabolomics as a tool to unveil plant–pathogen interactions. The untargeted approach is qualitative and gives a global profile of many unknown metabolites in a sample. The targeted approach is quantitative and more specific, as it aims for a determined class of known compounds.

Figure 3

Disease factors. Updated disease triangle into a pyramid, representing abiotic and biotic factors that interact with the pathogen and host to determine disease development as a function of time.

Figure 4

OMICs interaction. DNA and mRNA (red semi-circle) have a direct relationship with proteins (green semi-circle) and can be analyzed by genomics, transcriptomics and proteomics. Though metabolites (blue circle—which are analyzed by metabolomics) do not have a directly obvious relationship with specific genes and proteins, they are related in important ways that ultimately underlie phenotypes. The smaller arrows symbolize that indirect relationship, while the whole system is connected to phenotypes through the large arrow.