Involvement of phytohormones in root elongation activity of isoprothiolane in Arabidopsis.

Isoprothiolane (diisopropyl 1,3-dithiolan-2-ylidenemalonate, IPT), an active ingredient of "Fuji-one," has been used as a plant growth regulating agent to control non-parasitic damping-off (MURENAE disease) of rice seedlings. To understant plant growth regulating activity of IPT, its effect on root development was investigated in Arabidopsis. IPT enhanced root elongation at a lower concentration (12.5 µg/mL) but suppressed it at a higher concentration (75 µg/mL). Analysis using phytohormone-related mutants and chemical inhibitors revealed that the enhancement of root elongation by IPT required auxin, jasmonic acid, and ethylene signal transduction. Activation of the signal transduction mediated by these three phytohormones was confirmed by gene expression analysis. More detailed mechanisms of IPT's effect on root development were demonstrated via investigation using Arabidopsis and chemical inhibitors.