Similarly to BmToll9-1, BmToll9-2 Is a Positive Regulator of the Humoral Immune Response in the Silkworm, Bombyx mori
Jisheng Liu, Weijian Chen, Sina Chen, Shuqiang Li, Luc Swevers
Abstract
Toll receptors play important roles in the development and innate immunity of insects. Previously, we reported the immunological function of BmToll9-2 in silkworm, Bombyx mori, larvae. In this study, we focused on the role of BmToll9-2 as a regulator in the Toll signaling pathway. The expressions of most signaling genes in the Toll pathway, as well as immune effectors, were reduced after the RNAi of BmToll9-2. Coincidentally, hemolymph from BmToll9-2-silenced larvae exhibited decreased antibacterial activity in the growth of Escherichia coli, demonstrated either by growth curve or inhibitory zone experiments. The oral administration of heat-inactivated E. coli and Staphylococcus aureus following the RNAi of BmToll9-2 up-regulated the expression of most signaling genes in the Toll pathway and downstream immune effectors. The above results indicate that BmToll9-2 is positively involved in the Toll signaling pathway. As a positive regulator, BmToll9-2 is shown to be activated preferentially against E. coli and, in turn, positively modulates the humoral immune response in antibacterial activity.