Rotenone-sensitive mitochondrial potential in Phytomonas serpens: electrophoretic Ca2+ accumulation
Moyses, D.N. | Barrabin, H.
Phytomonas sp. are flagellated trypanosomatid plant parasites that cause diseases of economic importance in plantations of coffee, oil palm, cassava and coconuts. Here we investigated Ca2+ uptake by the vanadate-insensitive compartments using permeabilized Phytomonas serpens promastigotes. This uptake occurs at a rate of 1.13+/-0.23 nmol Ca2+ mg protein-1 min-1. It is completely abolished by the H+ ionophore FCCP and by valinomycin and nigericin. It is also inhibited by 2 micromolar ruthenium red, which, at this low concentration, is known to inhibit the mitochondrial calcium uniport. Furthermore, salicylhydroxamic acid (SHAM) and propylgallate, specific inhibitors of the alternative oxidase in plant and parasite mitochondria, are also effective as inhibitors of the Ca2+ transport. These compounds abolish the membrane potential that is monitored with safranine O. Rotenone, an inhibitor of NADH-CoQ oxidoreductase, can also dissipate 100% of the membrane potential. It is suggested that the mitochondria of P. serpens can be energized via oxidation of NADH in a pathway involving the NADH-CoQ oxidoreductase and the alternative oxidase to regenerate the ubiquinone. The electrochemical H+ gradient can be used to promote Ca2+ uptake by the mitochondria.Show more [+] Less [-]