Characterization of the superoxide dismutase (SOD) from the potato cyst nematode, Globodera pallida

Potato cyst nematodes (PCN), such as Globodera pallida and Globodera rostochiensis, are some of the most agriculturally and economically important pests of potato. Upon nematode infection, a principle component of plant defense is the generation of the reactive oxygen species (ROS). Reactive oxygen species are highly toxic molecules that cause damage to pathogens and host alike. In order to successfully infect the plant, nematodes protect themselves from ROS through the activation of their own antioxidant processes and ROS scavenging enzymes. One of these enzymes is a superoxide dismutase (SOD; EC 1.15.1.1), which prevents cellular damage by catalyzing conversion of the superoxide radical (O2-˙) to hydrogen peroxide (H2O2) and molecular oxygen (O2). We have isolated a putatively secreted isoform of a Cu-Zn superoxide dismutase (SOD-3) from G. pallida and localized the expression of this gene in the posterior region of the nematode. Furthermore, we studied the expression of the SOD-3 gene during early parasitic stages of infection (24-72h) in the susceptible potato cv. Desiree, resistant potato cv. Innovator, and an immune host, Solanum sisymbriifolium. SOD-3 gene was significantly upregulated, regardless of the host type, however, the expression pattern differed between the susceptible and the resistant or immune hosts. This suggests that SOD-3 gene is responding to infection in plant roots differently depending upon whether the nematode is experiencing a compatible or an incompatible interaction.