Cercospora beticola toxins. Use of fluorescent cyanine dye to study their effects on tobacco cell suspensions

Abstract

The fluorescent dye 3,3′-diethylthiadicarbocyanine iodide [diS-C 2-(5)] was used to observe plasmalemma transmembrane potential variations of tobacco cells treated with uncoupler (FCCP), respiratory inhibitors (azide and cyanide), and H +-ATPase inhibitors (DCCD and a carbanilate derivative). These chemicals induced an increase in fluorescence, indicating a dissipation of the transmembrane potential. The [diS-C 2-(5)] was also used to study the effects of two Cercospora beticola toxins on tobacco cells. Changes in fluorescence of [diS-C 2-(5)] suggested that these two toxins caused a dissipation of the transmembrane potential with a different magnitude whereas kinetics of their association with membranes were comparable.