RNAi-mediated silencing of an immune gene in Spodoptera littoralis (Lepidoptera, Noctuidae) alters its embryonic development

The Sl102 gene encodes a protein involved in the cellular immune response of Spodoptera littoralis. Knockdown of Sl102 gene in S. littoralis larvae increases the susceptibility to pathogens, providing the basis for the development of new insect pest control strategies. Here we explore the phenotypic effects of Sl102 gene silencing on embryonic development by soaking S. littoralis eggs in a dsRNA solution. The experimental results showed that gene silencing is associated with a drastic reduction in egg hatching and a very high mortality rate of the few hatched larvae. Structural and ultrastructural analyses showed morphological alterations in treated embryos indicating that the Sl102 gene, in addition to its immune function, has an important role in the regulation of embryonic development so far unrecognized, which is worth of further research efforts. This study contributes a novel member to the growing list of insect immune genes participating in other biological processes and offers the opportunity to exploit the pleiotropy between development and immunity for the setup of effective pest insect control strategies.