Study on the role of RPL23 gene in active immunity of termite Reticulitermes chinensis against Metarhizium anisopliae.

Ribosomal proteins are considered to be involved in the immunity of different animals against pathogens. The protein level of RPL23 increased after fungal infection in termites, but how it influence active immunity in termites is unknown. The role of RPL23 gene was studied to evaluate its impact on active immunity of termite Reticulitermes chinensis against entomopathogenic fungus (EPF) Metarhizium anisopliae. The RPL23 gene fragment (414 bp) was cloned and phylogenetic analysis revealed that it's very close to termite Coptotermes formosanus. Expression of RPL23 gene was significantly higher in abdomen as compared to thorax and head. Silencing RPL23 gene had no significant impact on the frequency and time of allogrooming towards fungus exposed termites from nestmates, which showed that nestmates acquired spores from infected termites through allogrooming. Expression of immune genes (GNBP1, GNBP2 and phenoloxidase) and apoptosis related genes (TNF-α, caspase 1, caspase 3 and caspase 8) decreased significantly in nestmates of fungus-treated termites after silencing of RPL23 gene as compared to control. Antifungal activity and survival of RPL23 silenced nestmates of fungus-treated termites also decreased. To sum up, this study found that silencing of RPL23 gene broke the active immunity against M. anisopliae infection, reduced the antifungal activity of termites, weakened cell apoptosis, and led to increased mortality of termites, which may help to find a potential alternative for chemical insecticides to control termites.