Abstract: 【Aim】 To explore the molecular mechanism by which vitellogenin (Vg) regulates the abundance of the symbiotic bacterium Rickettsia in Bemisia tabaci. 【Methods】 Female adult of B. tabaci MEAM1 was microinjected with dsRNA to conduct RNAi of BtVg, the expression levels of BtVg and the autophagy gene BtAtg8 in the female adult were detected by qRT-PCR, the mortality rate of female adults was recorded, and the abundance of Rickettsia in the female adult was quantified by qPCR. The localization and expression of BtVg and BtAtg8 in ovarioles and the abundance of Rickettsia in the ovarioles and midguts of the female adult were examined by immunofluorescence microscopy. After the autophagy induction by feeding the female adult of B. tabaci MEAM1 with the artificial diet containing rapamycin (10 μmol/L), the expression and localization of BtAtg8 in ovarioles were investigated by immunofluorescence microscopy and the abundance of Rickettsia in ovaries was detected by qPCR. 【Results】 The expression levels of BtVg and BtAtg8 in the female adult of B. tabaci MEAM1 were significantly decreased and significantly increased, respectively, the mortality rate of female adults of B. tabaci MEAM1 was significantly increased, the abundance of Rickettsia in the female adult of B. tabaci MEAM1 was significantly decreased, the expression levels of BtVg and BtAtg8 in ovarioles were obviously decreased and obviously increased, respectively, and the abundance of Rickettsia in the ovarioles and midgut obviously decreased at 3 d after microinjection of dsBtVg compared to the control (microinjected with dsGFP). The expression level of BtAtg8 in the ovarioles of the female adult of B. tabaci MEAM1 was increased significantly at 5 d after feeding with the artificial diet containing rapamycin (10 μmol/L), and the abundance of Rickettsia in the ovarioles of the female adult of B. tabaci MEAM1 was significantly decreased at 3 and 5 d after feeding with the artificial diet containing rapamycin (10 μmol/L) compared with the control fed with the artificial diet containing DMSO. 【Conclusion】 These results suggest that BtVg can protect Rickettsia from degradation by autophagy, and demonstrate the role of BtVg in regulating the abundance of Rickettsia in B. tabaci.

Key words: Bemisia tabaci, vitellogenin, autophagy; Rickettsia, autophagy gene, ovary