A novel DUF 3472 domain-containing fern protein impairs reproduction in Helicoverpa armigera

Helicoverpa armigera is a polyphagous field crop insect pest. It poses a major threat to economically important crops leading to significant financial losses globally. Given the escalating resistance cases against chemical and Bt-based insecticides, there is an urgent need to identify new molecules to control this insect through different modes of action. In this endeavour, we have isolated a new protein [named Msc42] efficacious to H. armigera from the fern Microsorum scolopendria. The protein has two domains of unknown function- DUF 5077 and DUF 3472. At an LC₅₀ of 3.6 μg/g, Msc42 severely impairs molting and metamorphosis in surviving larvae. Mass spectrometric analysis of the total soluble protein of larvae identified altered regulatory proteins responsible for impaired insect growth and reproduction. This includes larval cuticle proteins and endocuticle structural glycoproteins. Storage proteins were either at lower levels or below the detection threshold. Vitellogenins were also found deficient. The microscopic study showed that the fern protein ravaged ovarian follicle development leading to complete reproductive failure. Our results indicate that the novel fern protein Msc42 may offer an alternative strategy for controlling H. armigera.