Sick wings: the effects of the baculovirus AcMNPV on wing development in the speckled wood butterfly, Pararge aegeria

Baculoviruses not only affect resource allocation to growth and reproduction, but they also have the possibility to act on host signalling pathways involved in cell differentiation and thus tissue patterning. Infection typically starts in the insect gut after ingesting virally contaminated food, and the infection will spread to other tissues aided by, for example, metalloproteases. Metalloproteases, such as tolloid, regulate in normal host development the activity of the decapentaplegic (dpp) antagonist short gastrulation (sog). Dpp plays a key role in regulating wing shape, size and wing vein positioning. Overexpression of tolloid in Drosophila pupae results in wing abnormalities, especially in the posterior part of the wing, as it disturbs the balance between sog and dpp levels. It is known in Drosophila that bacteria that produce a number of different metalloproteases in their host, cause similar wing defects as when tolloid is overexpressed. The baculovirus AcMNPV produces the metalloprotease cathepsin (Ac-)v-cath. Cathepsin is not homologous to tolloid, but just as efficient a metalloprotease, and is known in flies to affect wing and leg imaginal discs outgrowth. Nothing is known, however, about how it affects wing shape and wing venation patterning. In this talk I will discuss in detail, at the phenotypic level, how wing development was affected in a series of experiments in which second instar speckled wood (Pararge aegeria) caterpillars were infected with different doses of AcMNPV. The implications of the effects of baculoviruses modulating wing development in natural populations will be discussed