Comparison of ceramide synthase inhibitors with other phytotoxins produced by Fusarium species

Fumonisin B₁ (FB₁), a phytotoxic secondary metabolite of Fusarium spp., was originally described as a mammalian toxin. Its mode of action in animals and plants is inhibition of ceramide synthase, an enzyme involved in sphingolipid biosynthesis. AAL-toxin, a structurally related long-chain alkylamine produced by Alternaria alternata, is phytotoxic to susceptible plants including asc/asc tomatoes, jimsonweed, and black nightshade. More recently, australifungin, a structurally unrelated compound produced by Sporormiella australis, was also shown to inhibit ceramide synthase. We observed a phytotoxicological course with australifungin that was different than that of fumonisin or AAL-toxin. AAL-toxin is a potential lead compound for the development of a novel bioherbicide because no currently available herbicide uses inhibition of ceramide synthase as its mechanism of action. With the objective of developing safe and effective herbicides, we tested analogs of FB₁ and AAL-toxin in a program aimed at discovering compounds that retain phytotoxicity but have reduced or no mammalian toxicity. We also observed phytotoxicity in other Fusarium spp. secondary metabolites including moniliformin, fusaric acid, gibberellic acid, and 2,5-anhydro-D-glucitol.