A Plant-Derived Antifungal Agent, Poacic Acid, Inhibits Germination and Tube Growth of Lily Pollen

Poacic acid is a novel natural antifungal agent. It inhibits the growth of fungal cells, including budding yeast Saccharomyces cerevisiae, by inhibiting the synthesis of β-1,3-glucan, which is a major component of the fungal cell wall. Although poacic acid is expected to be a candidate pesticide owing to its antifungal activity, its effects on plant cells have not been investigated. In this study, we analyzed the effects of poacic acid on lily (Lilium longiflorum) pollen. Poacic acid inhibited lily pollen germination and tube growth at concentrations lower than those that inhibited budding yeast growth. While poacic acid did not inhibit callose (β-1,3-glucan) synthesis in pollen tubes, it inhibited membrane traffic, including endocytosis and secretion, and the organization of the actin cytoskeleton within pollen tubes. Since these processes have been shown to play essential roles in pollen tube growth, our study indicates that poacic acid affects lily pollen tube growth differently than it affects budding yeast. Poacic acid also inhibited the growth of Arabidopsis thaliana pollen tubes and root.