Spearmint targets microtubules by (-)-carvone

Allelopathy can provide sustainable alternatives to herbicides because it is based on specific signals rather than generic toxicity. We show that the allelopathic activity of Spearmint and Watermint is linked with their main compounds, (-)-carvone and (+)-menthofuran, both deriving from (-)-limonene. Germination of Poppy and Cress, and root growth of Arabidopsis thaliana are inhibited by very low concentrations of (-)-carvone, acting even through the gas phase. (+)-Menthofuran is active as well, but at lower efficacy. Using fluorescently tagged marker lines in tobacco BY-2 cells and Arabidopsis roots, we demonstrate a rapid degradation of microtubules and a remodeling of actin filaments in response to (-)-carvone and, to a milder extent, to (+)-menthofuran. This cytoskeletal response is followed by cell death. By means of a Root Chip system, we can follow the tissue dependent response of the cytoskeleton and show a cell-type dependent gradient of sensitivity between meristem and distal elongation zone, accompanied by programmed cell death.