Imaging Plant Lipids with Fluorescent Reporters

Abstract

In plants, lipids function as structural elements and signaling molecules. Understanding lipid composition and dynamics is essential for unraveling their biological functions and metabolism. Mapping the spatiotemporal distribution of lipids in plants holds great potential for elucidating lipid biosynthetic pathways and gaining insights to guide crop genetic engineering. Recent progress in fluorescence microscopy and imaging has opened new opportunities for researchers to visualize plant lipids in vivo at high spatiotemporal resolution. In this review, we provide an up-to-date overview of the methods used to image plant lipids with fluorescence microscopy. We highlight caveats and potential limitations of these approaches and provide suggestions for optimizing their utilization. This review synthesizes current knowledge and highlights the potential of these methods to provide new insights into lipid biology.

Keywords: biosensor; fluorescence; plant lipids; spatiotemporal dynamics; visualization.

Figure 1

Representative aromatic fluorescent dyes used in plant studies. DI-4-ANEPPDHQ and Laurdan are phase-sensitive membrane probes whose emission spectra exhibit a significant blueshift in the lipid-ordered phase compared with the disordered phase. Nile Red is used to localize and quantitate lipids, particularly neutral lipid droplets within cells. The membrane probes DPH and TMA-DPH are located in the bilayer core and at the interfacial region, respectively. Additional details on the binding specificities of these dyes can be found in Table 1.

Figure 2

Typical fluorescent lipid analogs utilized in plant studies and their precursors. (a) BODIPY-PC incorporated into cells functions as a substrate to generate BODIPY-labelled lipid products. (b) Carboxy-DCFDA is colorless and nonfluorescent until the acetate groups are cleaved by intracellular esterases to yield the fluorescent fluorophore. This property makes it a useful tool for visualizing cellular compartments where the intracellular esterases work.

Figure 3

Schematic of the localizations of the activities of various fluorescent molecules. Fluorescent dyes are displayed as simple shapes with labels in purple type. Lipid analogs are represented by colored polygons connected to a circle with blue labels. Genetically encoded biosensors are shown as hexagons with two arms and brown labels. Electrostatic biosensors are fluorescent proteins fused to a carboxy (C)-terminal lipid anchor in conjunction with an adjacent unstructured peptide of varying net positive charge, which makes them able to interact with the membrane (negatively charged by lipids). The major positional information of the probes is shown. GN, Golgi network. MT, mitochondrion. CT, chloroplast. LD, lipid droplet. Lop, liquid-ordered phase. Ldp, liquid-disordered phase.