Effects of eutypine, a toxin from Eutypa lata, on plant cell plasma membrane: Possible subsequent implication in disease development

Eutypine, 4-hydroxy-3-(3-methyl-3-butene-1-ynyl) benzaldehyde, is a toxin produced by Eutypa lata, the causal agent of eutypa dieback. An essential target of eutypine action lies at the plasmalemma as shown by the data obtained during this study on three experimental models (Beta vulgaris, Mimosa pudica, Vitis vinifera). The fungal toxin at 100 μM triggered a rapid dose-dependent hyperpolarization of the membrane potential in M. pudica pulvinar cells. It also enhanced proton permeability in plant tissues or in purified plasma membrane vesicles (PMV) without modification of the H+-ATPase activity. As a physiological consequence, eutypine hindered sucrose and valine absorption by PMV and plant tissues. In all these situations, eutypine behaved like a protonophoric compound, such as dinitrophenol (DNP) used at 10 μM, and acted specifically since eutypinol, an inactive derivative, only triggered very limited effects at a 100-μM concentration. Eutypine did not modify phenylalanine ammonia lyase (PAL, EC 4.3.1.5) activity, suggesting that its toxic action has no after-effect on the secondary metabolism.