Click chemistry reagents act as probes to label metabolic pathways in interkingdom interactions
Illustration by Cortland Johnson and Natalie Sadler | Pacific Northwest National Laboratory
Chemical and biochemical signals are at the heart of interactions between plants and microbes. Those signals include information about nutrient signaling and acquisition; cues for growth and development; and defense and immune responses. Chemical biology provides a variety of tools and approaches to explore the fundamental molecular mechanisms driving these complex interactions between organisms in different kingdoms. A new article reviews bio-orthogonal click chemistry reagents that can be used as probes to label metabolic pathways in plants and microbes. Labeling reagents incorporated into live cells, tissues, or whole organisms can be tracked spatially using fluorescence imaging, as well as temporally using pulse-chase methods.
Activity-based probes label enzymes based on their specific mechanisms of action. This allows scientists to characterize protein function even in complex samples, such as a microbiome, or samples with little pre-existing knowledge of functional potential. Much of the work described in this review uses chemical probes to study how plant-associated microbes influence plant metabolism of sugars, phospholipids, and other structural molecules. Other probes target plant proteins involved with immune responses to pathogens. Additional development of chemical probes for key signaling molecules and plant hormones will help scientists learn how microbes promote plant growth as well.
Metabolic labeling of live microbes and plant tissues with azide- or alkyne-modified glycan, monolignol, lipid, or amino acid substrates enables click chemistry attachment of various tags for imaging or affinity enrichment. Alkynes are generally better tolerated in plants than azido reagents.
For imaging applications, scientists can track fluorescently labeled probes through plant tissue, with subcellular resolution of structures such as the cell walls of roots. Other probes enable scientists to track enzyme activity before and after infection with a pathogen, revealing protein functions involved with plant immune responses.
Challenges remain for applying activity-based probes to plant–microbe systems, including adapting them to systems in natural soils and delivering probes to live plant tissues.
Vivian S. Lin
Pacific Northwest National Laboratory
vivian.lin@pnnl.gov
Preparation of this manuscript was funded in part by a grant from the Laboratory Directed Research and Development Program of Pacific Northwest National Laboratory.
Published: April 21, 2021
V.S. Lin, “Interrogating Plant-Microbe Interactions with Chemical Tools: Click Chemistry Reagents for Metabolic Labeling and Activity-Based Probes.” Molecules 26, 243 (2021). [DOI: 10.3390/molecules26010243]