Suppression of Vitellogenin and Ultraspiracle in honey bee fat body influences the gustatory responsiveness and starvation resistance by affecting glucose metabolism and endocrine physiology

BACKGROUND: The sterile honey bee worker varies in a series of behavioral traits including gustatory responsiveness, age of onset of foraging, and foraging bias towards pollen or nectar. It has been demonstrated that vitellogenin, an egg-yolk protein precursor, is a behavior affector directly influencing the worker foraging behavior. In addition, it has been shown that juvenile hormone (JH) and ultraspiracle gene (USP) is involved in this behavioral physiology. METHODS: In this study, we performed two genes, vitellogenin and USP, double knockdown in the newly emerged bee as well as vitellogenin and USP single gene knockdown. First, we observed effects of different gene perturbations on the worker behavior and starvation resistance. In order to explain the phenotypes we observed mechanistically, we tested JH level and glucose titer in hemolymph and measured lipid storage in fat body. At last, we looked at transcript abundances in fat body for several candidate genes. RESULTS&DISCUSSION: Our results showed bees with double knockdown responded to starvation differently and had higher gustatory responsiveness. Double-knockdown bees had higher glucose and JH titers in hemolymph. The fat body gene expression of PKG and ilp2 was down-regulated in double-knockdown bees. These results support that insulin signaling pathway, PKG related glucose metabolic pathway and endocrine hormone are involved in this behavioral physiology in response to the perturbations of vitellogenin and USP.