Salicylate Glucoside as a Nontoxic Plant Protectant Alternative to Salicylic Acid

Salicylic acid (SA) is a phytohormone essential for plant defense and development. Exogenously applied SA protects crops from abiotic and biotic stresses and improves yield. However, SA at higher concentrations induces cell death. Here, we test if a naturally occurring SA conjugate, salicylate glucoside (SAG), can be used as a nontoxic plant protectant. We show that Arabidopsis leaves treated with 5 mM SAG neither decreased chlorophyll content nor accumulated reactive oxygen species (ROS), contrary to SA-treated samples. Furthermore, externally applied SAG did not induce the expression of pathogenesis-related genes. When infected by Pseudomonas syringae, SAG-treated Arabidopsis showed a 97% ± 1.1% reduction of bacterial counts compared to the control. In conclusion, surface-applied SAG has the potential to be used as a nontoxic crop protectant against various stresses. Recent high-titer production of SAG in engineered Escherichia coli makes this compound accessible for agricultural applications.