C. Deswarte et al., TRANSPORT, CYTOPLASMIC ACCUMULATION AND MECHANISM OF ACTION OF THE TOXIN EUTYPINE IN VITIS-VINIFERA CELLS, Journal of plant physiology, 149(3-4), 1996, pp. 336-342
The mechanism of the toxic action of eutypine, 4-hydroxy-3-(3-methyl-3
-butene-1-ynyl) benzaldehyde, a toxin produced by the fungus Eutypa la
ta, the agent of dying arm disease of the grapevine, was investigated
with cell suspension cultures of Vitis vinifera cv. Gamay and C-14-lab
elled eutypine. The study of the chemical characteristics of eutypine
revealed that the toxin is a weak acid (pKa = 6.2), which also has a l
ipophilic character (water/octanol partition coefficient of 86). Eutyp
ine was rapidly taken up by the cells and accumulated against a concen
tration gradient. Uptake showed no saturation at high eutypine concent
ration, and neither structural analogues of eutypine nor protein modif
ying reagents had an inhibitory effect on eutypine uptake. These data
suggest a mechanism of passive diffusion for eutypine uptake. The euty
pine accumulation observed in cells can be partly explained by an ion
trapping mechanism related to the ionization state of the toxin. It ha
s been demonstrated that some eutypine molecules insert into cellular
lipids, i.e. cell membranes. Such partition of eutypine in the cells m
ight play a major role in the expression of its toxicity. Eutypine see
ms to affect the functioning of mitochondria by an uncoupling effect o
r by inhibiting succinate dehydrogenase activity. These results sugges
t that eutypine has the same properties as the uncoupling agents that
act as mobile proton carriers. The reduction of the energetic charge f
ollowing eutypine action could explain the symptoms observed in diseas
ed plants.