Rapid increase in the frequency of a novel mutation in the β2-octopamine receptor potentially associated with amitraz resistance in Korean populations of Varroa mites

Monday, November 11, 2024

9:24 AM – 9:36 AM MST

Location: Phoenix Convention Center, 126 A, PCC

Presenting Author(s)

JL

Joon Hee Lee

Seoul National University
Seoul, Seoul-t'ukpyolsi, Republic of Korea

Co-Author(s)

SL

SI Hyeock Lee

Seoul National University
Seoul, Seoul-t'ukpyolsi, Republic of Korea
Susie Cho (she/her/hers)

PhD Student
Seoul National University
Gwanak-gu, Seoul-t'ukpyolsi, Republic of Korea
YK

Young Ho Kim

Professor
Kyungpook National University
Sangju, Kyongsang-bukto, Republic of Korea
SK

Sanghyeon Kim

University of Florida
Gainesville, Florida
EY

Euijin You

Kyungpook National University
Sangju, Kyongsang-bukto, Republic of Korea
YL

Youngcheon Lim

Seoul National University
Seoul, Seoul-t'ukpyolsi, Republic of Korea

The Varroa mite, Varroa destructor, is a significant pest affecting honey bees and contributing to colony collapse disorder. In Korea, amitraz has been extensively used as an alternative acaricide due to fluvalinate resistance in recent years. To monitor potential development of amitraz resistance in Korean populations of Varroa mites, we analyzed the frequencies of two known mutations (N87S and Y215H) in the β2-octopamine receptor, which are associated with amitraz resistance, in mite samples collected from 2020 to 2024. Neither of these mutations were found; however, a novel mutation (T115N) was identified. Interestingly, the frequency of this novel mutation increased rapidly over the examined periods. Homology modelling, using the human adrenaline receptor sequence as a template, indicated that the T115 residue is part of the ligand binding domain, suggesting that its substitution with a radical amino acid such as Asn likely affects the amitraz affinity, potentially resulting in resistance. To confirm the role of the T115N mutation in amitraz resistance, we investigated the time-dependent intoxication responses of a Varroa mite population with an average T115N mutation frequency of 50% following treatment with a diagnostic dose of amitraz. When analyzing the genotypes at the T115 residue, all mites exhibiting early intoxication symptoms had the homozygous susceptible allele (T115), whereas most mites surviving 24 h post-treatment had the homozygous resistant allele (N115). These finding, along with the homology modeling data, suggest that the novel T115N mutation confers amitraz resistance and is likely specific to Korean populations of Varroa mites.