Functional characterization of knockdown resistance mutations in the plant bug, Apolygus lucorum Meyer-Dür

Apolygus lucorum could cause severe economic damage to crops in China. The pest has been controlled by pyrethroids, and the target of pyrethroids is voltage-gated sodium channel (Na_v). Double mutation (L¹⁰⁰²F/D⁹⁴¹G) was detected in a field-strain of A. lucorum . We found there was single mutation L¹⁰⁰²F and double mutation L¹⁰⁰²F/D⁹⁴¹G, but no single mutation D⁹⁴¹G in the field. The tail currents of L¹⁰⁰²F and L¹⁰⁰²F/D⁹⁴¹G were reduced by two types pyrethroid. In contrast, D⁹⁴¹G showed a similar activity as wild type channel. D⁹⁴¹G and L¹⁰⁰²F are both located in domain II but do not face the pyrethroid-binding pocket directly, suggesting that they might affect the insecticide-binding allosterically. L¹⁰⁰²F/D⁹⁴¹G has significantly different responses to pyrethroids compared to the wild type, but D⁹⁴¹G alone has little effect compared to wild type. Our finding demonstrates that some mutation do not cause resistance by itself but can enhance the resistance combined with other mutations.