The effect of entomopathogenic fungi Metarhizium robertsii of different virulence on the generation of reactive oxygen species in Galleria mellonella larvae

Abstract

The toxicity of reactive oxygen species (ROS) plays a significant role in the immune response of insects. Little is known about the effect of the virulence of entomopathogenic fungi on the generation of ROS in a host. The aim of the study was to reveal whether the different levels of virulence cause the different ROS production in insects. The half-lethal dosages of two Metarhizium robertsii strains, of high and low virulence, which have shown a similar survival to Galleria mellonella larvae after treatment, were used in the study. The rates of ROS generation were determined in the cuticle, hemocytes and cell-free hemolymph of G. mellonella larvae 1, 3, 5 days after fungi treatment. We have shown that the level of ROS production in the cuticle and hemolymph of G. mellonella larvae depends on the virulence of the M. robertsii strains. The influence of both fungal strains on the rate of ROS formation in hemocytes was the same throughout the observation period. The host’s defense mechanism was activated in the cuticle under the treatment of both low and high virulent fungi strains. In the hemolymph, the activation of the immune response occurred only after treatment with low virulent strain.