Abstract
Though Helminthosporium maydis race T (HmT) toxin decreased active Ca2+ uptake into mitochondria isolated from susceptible (T) but not resistant (N) corn (Kimber, Sze, 1984 Plant Physiol 74: 804-809 the mode of toxin action is not understood. This study shows that HmT toxin or A23187 (a Ca2+ ionophore) dissipated a Ca2+ gradient in T mitochondria. However, HmT toxin had no effect on Ca2+ gradients in N mitochondria or microsomal vesicles from T or N corn. The results suggest that HmT toxin increased membrane permeability to Ca2+ in mitochondria of T corn specifically.