Mode of Action of the Natural Product Allicin in a Plant Model: Influence on the Cytoskeleton and Subsequent Shift in Auxin Localization

Allicin is a defense substance produced by garlic cells when they are injured. It is a redox-active thiosulfinate showing redox-activity with a broad range of dose-dependent antimicrobial and biocidal activity. It is known that allicin efficiently oxidizes thiol-groups, and it has been described as a redox toxin because it alters the redox homeostasis in cells and triggers oxidative stress responses. Allicin can therefore be used as a model substance to investigate the action of thiol-specific prooxidants. In order to learn more about the effect of allicin on plants, we used pure synthetized allicin, and studied the influence of allicin on organelle movement in Tradescantia fluminensis as a cytoskeleton-dependent process. Furthermore, we investigated cytoplasmic streaming in sterile filaments of Tradescantia fluminensis, organelle movement using transgenic Arabidopsis with organelle-specifics GFP-tags, and effects on actin and tubulin in the cytoskeleton using GFP-tagged lines. Tubulin and actin were visualized by GFP-tagging in transgenic lines of Arabidopsis thaliana to visualize the influence of allicin on the cytoskeleton. Since auxin transport depends on recycling and turnover of the PIN protein involving cytoskeletal transport to and from the membrane localization sites, auxin distribution in roots was investigated using of transgenic PIN1–GFP, PIN3–GFP, DR5–GFP and DII–VENUS Arabidopsis reporter lines. Allicin inhibited cytoplasmic streaming in T. fluminensis, organelle movement of peroxi-somesperoxisomes, and the Golgi apparatus in a concentration-dependent manner. It also destroyed the correct root tip distribution of auxin, which probably contributed to the observed inhibition of root growth. These observations of the disruption of cytoskeleton-dependent transport processes in plant cells add a new facet to the mechanism of action of allicin as a redox toxin in cells.