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1 October 2012 Concentration-Dependent Effects of GABA on Insensitivity to Fipronil in the A2′S Mutant RDL GABA Receptor From Fipronil-Resistant Oulema oryzae (Coleoptera: Chrysomelidae)
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Abstract

The beetle Oulema oryzae Kuwayama (Coleoptera: Chrysomelidae), an important pest of rice, has developed fipronil resistance in Japan. Molecular cloning and sequence analysis of O. oryzae RDL γ-aminobutyric acid (GABA) receptor subunit (OO-RDL) genes from fipronil-susceptible and -resistant O. oryzae identified the A2′S mutation (index number for the M2 membrane-spanning region). To investigate the effect of the A2′S mutation on fipronil resistance, we stably expressed the wild-type and mutant OO-RDL homomers in Drosophila Mel-2 cells. A membrane potential assay exhibited that the IC50 values of fipronil for inhibition of the response to EC80 GABA of the wild-type and A2′S mutant OO-RDL homomers were 0.09 µM and 0.11 µM, respectively. However, the IC50 values of fipronil for inhibition of the response to EC95 GABA of the wild-type and A2′S mutant OO-RDL homomers were 0.11 µM and ≈5 µM, respectively. These results suggest that the GABA concentration is an important factor affecting fipronil resistance in O. oryzae carrying the A2′S mutation in OO-RDL.

© 2012 Entomological Society of America
Toshifumi Nakao, Atsuko Naoi, Masako Hama, Nobuyuki Kawahara, and Kangetsu Hirase "Concentration-Dependent Effects of GABA on Insensitivity to Fipronil in the A2′S Mutant RDL GABA Receptor From Fipronil-Resistant Oulema oryzae (Coleoptera: Chrysomelidae)," Journal of Economic Entomology 105(5), 1781-1788, (1 October 2012). https://doi.org/10.1603/EC12073
Received: 16 February 2012; Accepted: 1 July 2012; Published: 1 October 2012
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