Isotopic Labeling Analysis using Single Cell Mass Spectrometry

Here we show that a recently developed single cell mass spectrometry method can be used to monitor the incorporation of an isotopically labeled precursor into single plant protoplasts. Specifically, we show that we can monitor the incorporation of deuterium-labeled tryptamine into an alkaloid pathway over the course of 24 hours. The resulting data provides a glimpse into the rate of synthesis and transport of chemically complex monoterpene indole alkaloids in single cells across a small population. By measuring the concentration of labeled alkaloids, we gain insight into the flux of an important plant biosynthetic pathway. Stable-isotope labeling is a widely used approach to study metabolic networks by tracking isotopologues over time. This manuscript provides proof of principle that single cell isotopic labeling can be performed in plant pathways.