Novel application of 2-[18F]fluoro-2-deoxy-D-glucose to study plant defenses

Introduction: Since its first use in humans in 1976, 2-[18F]fluoro-2-deoxy-D-glucose (18FDG) continues to serve as a tracer to measure tissue glucose metabolism in medical imaging. Here we demonstrate a novel use for this tracer to study glycoside biosynthesis in plants as a measure of plant response to defense induction. Methods: Coupling autoradiography with radio high-performance liquid chromatography analysis of tissue extracts, we examined the combined effects of leaf wounding and treatment using the potent plant defense hormone, methyl jasmonate (MeJA), to measure tracer distribution and tracer use in secondary defense chemistry in Arabidopsis thaliana. We hypothesized that competing sinks like roots and reproductive tissues, as well as vascular architecture, would impact the induction of phenolic defenses of the plant that make use of glucose in glycoside formation by altering distribution and metabolic utilization of 18FDG. Results: Our studies showed that leaf orthostichy defined the major route of 18FDG transport in both vegetative and reproductive plants when a single petiole was cut as the entry point for tracer introduction. However, when nonorthostichous leaves were damaged and treated with MeJA, 18FDG was transported in its intact form to these leaves 3 h later, where it was incorporated into phenolic glycosides. Conclusions: Our work demonstrates a new use for 18FDG in plant science with insights into carbohydrate allocation that contradict conclusions of previous studies showing transport of resources away from damaged sites.