# Reversible Chemogenetic Fluorescence Labeling with pFAST in C. elegans

## TL;DR

Researchers developed a reversible, multicolor fluorescence labeling system in C. elegans using pFAST, which can be turned on and off with specific chemicals.

## Contribution

The study introduces td-pFAST as a novel tool for reversible and multicolor chemogenetic labeling in C. elegans tissues.

## Key findings

- td-pFAST in C. elegans pharyngeal muscle showed rapid lime fluorogen activation and quenching with darth.
- Amber and coral fluorogens enabled reversible multicolor labeling with distinct emission spectra.
- Fluorogen delivery via soaking failed due to cuticle permeability limitations in intact worms.

## Abstract

The promiscuous fluorescence-activating and absorption-shifting tag (pFAST) enables reversible chemogenetic labeling with multiple fluorogens. We generated a single-copy tandem pFAST (td-pFAST) transgenic

Caenorhabditis elegans

strain expressed in pharyngeal muscle. In dissected worms, lime fluorogen produced rapid fluorescence that was efficiently quenched by the competing ligand darth, demonstrating reversibility. Amber and coral fluorogens also produced reversible signals with distinct emission spectra, supporting multicolor labeling. However, fluorogen delivery by soaking intact worms failed, indicating cuticle permeability remains a barrier. These findings establish td-pFAST as a functional probe for reversible, multicolor labeling in dissected

C. elegans

tissues.