Changes in host plasma membrane ion fluxes during the Gomphrena globosa-papaya mosaic virus interaction

grantor: University of TorontoPapaya mosaic virus (PMV) is a single-stranded RNA virus that belongs to the potexvirus family, which produces a localised infection on Gomphrena globosa. In G. globosa, necrotic lesions surrounded by a chlorotic ring develop on the inoculated leaf, however, the rest of the plant remains healthy. The lesions in this interaction are thought to be the result of a non-host hypersensitive response (HR) resulting in resistance to the virus by limiting its spread to the rest of the plant. In this study the patch-clamp technique was used to elucidate the early events that occur during this non-host HR to PMV. Preliminary results using whole cell recordings demonstrated that addition of virus to the cell caused a decrease in the average inward currents (i.e. Ca$\sp{2+}$ moving into the cell or gluconate moving out of the cell) and an increase in the outward currents (i.e. Cl$\sp-$ moving into the cell and/or K$\sp+$ moving out of the cell). The increase in the average outward currents observed when PMV was present inside the patched cell was dependent on the PMV concentration used and was saturated at 2.5 $\mu$g/ml of PMV. In this study, it was shown that tobacco mosaic virus (TMV) infection of G. globosa also produced local lesions similar to those caused by PMV. Moreover, TMV addition to G. globosa protoplasts produced similar changes in the average ion currents as PMV/G. globosa interaction. This is the first time that changes in ion fluxes were characterised during a plant-virus interaction. The observed changes in average ion currents may represent an early event in the signal transduction pathway leading to the development of non-host resistance in the PMV-G. globosa interaction.M.Sc