Immune defense mechanism of Reticulitermes chinensis (Snyder) (Blattodea: Isoptera) against Serratia marcescens Bizio

Reticulitermes chinensis (Snyder) is an important pest species in China. Serratia marcescens Bizio (SM1) is a potent biological bacterium. In our lab, we found that SM1 can kill R. chinensis. To date, the interaction between R. chinensis and SM1 has not been studied. Here, we explored immune re-sponses of R. chinensis against SM1 using transcriptome sequencing. To elucidate immune-related genes, we identified 126,153 unigenes from R. chinensis. In total, 178 immune-related differentially expressed genes (DEGs) were identified. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that many cellular responses were enriched in the top 20 terms. Then, we sys-tematically analyzed several cellular immune pathways involved in the response of R. chinensis to SM1, including phagocytosis, autophagy and endocytosis pathways. Next, the regulation profiles of the immune-related genes were assessed using qRT-PCR, and the expression levels of the se-lected genes were upregulated. Further results revealed SM1-mediated activation of humoral immune responses genes, including Toll, IMD and melanization pathways, which suggested the involvement of humoral immune responses in the defense against SM1. This research elucidated the mechanisms underlying the immune defense of R. chinensis against SM1, providing a solid theoretical basis for exploiting new immune-suppressive agents to control R. chinensis. Moreover, this study will facilitate the better control of R. chinensis using SM1.