Abstract: 【Aim】 This study aims to analyze the effect of sodium channel auxiliary subunits on the sodium channel function in Rhopalosiphum padi, and to explore the roles of auxiliary subunits in the gating properties of sodium channel. 【Methods】 The expression levels of five sodium channel auxiliary subunit genes (RpTEH1, RpTEH2, RpTEH3, RpTEH4 and RpTipE) in R. padi adults after RNAi of sodium channel genes RpNa_vH1 and RpNa_vH2 by microinjection of dsRpNa_vH1 and dsRpNa_vH2, respectively, were detected by real-time quantitative PCR (qRT-PCR), the effects of RNAi of RpTipE on the expression levels of genes of sodium channels and their auxiliary subunits in R. padi adults and the susceptibility of these adults to LC₅₀ of beta-cypermethrin were determined by qRT-PCR and insecticide bioassay, respectively, and the Na⁺ currents in Xenopus laevis oocytes evoked by the Drosophila sodium channel gene DmNa_v22 cRNA injected alone and DmNa_v22 cRNA co-injected with cRNAs of the sodium channel auxiliary subunit genes DmTipE of Drosophila, and RpTEH2, RpTEH3, RpTEH4 and RpTipE of R. padi, respectively, were detected by the two-electrode voltage clamp technology to analyze the function of sodium channel auxiliary subunits of R. padi. 【Results】 Knockdown of the sodium channel gene RpNa_vH1 of R. padi by RNAi significantly reduced the expression levels of four sodium channel auxiliary subunit genes (RpTEH1, RpTEH2, RpTEH3 and RpTipE) in R. padi adults， whereas showed no significant influence on the expression level of RpTEH4. Knockdown of the sodium channel gene RpNa_vH2  of R. padi by RNAi significantly reduced the expression levels of the sodium channel auxiliary subunit genes RpTEH1, RpTEH2, RpTEH3, RpTEH4 and RpTipE. The expression levels of the sodium channel genes RpNa_vH1 and RpNa_vH2 and the sodium channel auxiliary subunit genes RpTEH1, RpTEH2, RpTEH3 and RpTEH4 were significantly reduced after knockdown of the sodium channel auxiliary subunit gene RpTipE of R. padi by RNAi. The susceptibility of R. padi adults to LC₅₀ of beta-cypermethrin was significantly decreased at 48 h after RNAi of RpTipE. The two-electrode voltage clamp recording showed that co-injection of DmNa_v22 cRNA with cRNAs of the sodium channel auxiliary subunit genes RpTEH2, RpTEH3, RpTEH4 and RpTipE of R. padi, respectively, in X. laevis oocytes increased the Na⁺ current of Drosophila sodium channel DmNa_v22. 【Conclusion】 Sodium channel auxiliary subunits may be involved in regulating the gating properties of sodium channels in R. padi.

Key words: Rhopalosiphum padi, sodium channel, sodium channel auxiliary subunits, electrophysiological experiments, RNAi, gene expression