Jianghong Li, Matthew C. Heerman, Jay D. Evans, Robyn Rose, Wenfeng Li, Cristina Rodriguez-Garcia, Gloria DeGrandi-Hoffman, Yazhou Zhao, Shaokang Huang, Zhiguo Li, Michele Hamilton, and Yanping Chen
Nutrition is involved in regulating multiple aspects of honeybee biology such as caste, immunity, lifespan, growth and behavioral development. Deformed wing virus (DWV) is a major pathogenic factor which threatens honeybee populations, and its replication is regulated by nutrition status and immune responses of honeybees. The alimentary canal of the honeybee is home to a diverse microbial community that provides essential nutrients and serves to bolster immune responses. However, to what extent gut bacteria affect honeybee nutrition metabolism and immunity with respect to DWV has not been investigated fully. In this study, newly emerged worker bees were subjected to four diets that contained 1) pollen, 2) pollen and antibiotics, 3) neither pollen nor antibiotics, 4) antibiotics alone. The expression level of two nutrition genes target of rapamycin (tor) and insulin like peptide (ilp1), one nutritional marker gene vitellogenin (vg), five major royal jelly proteins genes (mrjp1-5), one antimicrobial peptide regulating gene relish (rel), and DWV virus titer and its replication intermediate, negative RNA strand, were determined by qRT-PCR from the honeybees after 7 days post antibiotic treatment. Additionally, honeybee head weight and survival rate were measured. We observed that antibiotics decreased the expression of tor and rel, increased DWV titer and its replication activity. Expression of ilp1, five mrjps, vg, and honeybee head weight were also reduced compared to bees on a pollen diet. Antibiotics also caused a significant drop in survivorship, which could be rescued by addition of pollen to diets. Of importance, pollen could partially rescue the loss of vg and mrjp2 while also increasing head weight of antibiotic-treated bees. Our results illuminate the roles of bacteria in honeybee nutrition, metabolism, and immunity; which confer the capability of inhibiting virus replication, extending honeybee lifespan, and improving overall health.