Laboratory of Agrozoology, Department of Plants and Crops, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, 9000 Ghent, Belgium; Department of Plant Protection, Faculty of Agriculture, Ankara University, Diskapi, 06110, Ankara, Türkiye.
Laboratory of Agrozoology, Department of Plants and Crops, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, 9000 Ghent, Belgium.
Pestic Biochem Physiol. 2024 Sep;204:106080. doi: 10.1016/j.pestbp.2024.106080. Epub 2024 Aug 8.
Varroa destructor is widely recognized as a significant contributor to colony collapse disorder. Chemical acaricides, such as amitraz, have been extensively used for Varroa control due to their selectivity within beehives. However, the increasing number of cases of amitraz resistance across global V. destructor populations poses a significant challenge. In this study, we conducted a comprehensive molecular screening of the β-adrenergic-like octopamine receptor (Octβ2R), the target-site of amitraz, across 66 Turkish and 63 Belgian V. destructor populations. Although previously reported amitraz resistance mutations were not detected, the screening revealed a novel Y337F mutation located within transmembrane 7 (TM7) of Octβ2R in Turkish Varroa populations. Notably, this mutation was identified in the last residue of the highly conserved NPxxY motif associated with the activation of G-protein coupled receptors (GPCR). Among the 66 Varroa samples from Türkiye, twenty harbored the Y337F mutation, with eight samples exhibiting fixation of the mutation. Subsequent bioassays revealed over 8-fold resistance to amitraz in populations that contain the Y337F mutation. Genotyping of mites after exposure to 10 mg a.i./l amitraz demonstrated that all surviving mites were homozygous for the Y337F mutation, whereas dead mites carried susceptible alleles, providing genetic linkage between mutation and phenotype. Further, we used CRISPR-Cas9 editing to introduce the Y337F mutation in the orthologous Octβ2R of the model organism Tetranychus urticae. Crispants exhibited over threefold resistance to amitraz. In conclusion, this study identified and validated a novel amitraz resistance mutation. Additional research is required to further evaluate the phenotypic strength of Y337F in the context of operational resistance with current treatment strategies.
瓦螨（Varroa destructor）被广泛认为是导致蜂群崩溃失调的重要因素。由于其在蜂箱内的选择性，化学杀螨剂如咪丙环虫酯（amitraz）已被广泛用于瓦螨的防治。然而，全球范围内瓦螨种群对咪丙环虫酯的抗药性不断增加，这是一个重大挑战。在这项研究中，我们对 66 个土耳其和 63 个比利时瓦螨种群的β-肾上腺素样章鱼胺受体（Octβ2R）进行了全面的分子筛选，Octβ2R 是咪丙环虫酯的靶标。尽管没有检测到先前报道的咪丙环虫酯抗性突变，但筛选结果显示，在土耳其瓦螨种群的 Octβ2R 跨膜 7（TM7）内发现了一个新的 Y337F 突变。值得注意的是，该突变位于与 G 蛋白偶联受体（GPCR）激活相关的高度保守 NPxxY 基序的最后一个残基。在来自土耳其的 66 个瓦螨样本中，有 20 个样本携带 Y337F 突变，其中 8 个样本显示突变的固定。随后的生物测定显示，含有 Y337F 突变的种群对咪丙环虫酯的抗性超过 8 倍。暴露于 10mg a.i./l 咪丙环虫酯后对螨虫进行基因分型表明，所有存活的螨虫均为 Y337F 突变的纯合子，而死亡的螨虫携带敏感等位基因，突变与表型之间存在遗传连锁。此外，我们使用 CRISPR-Cas9 编辑技术在模式生物二斑叶螨（Tetranychus urticae）的同源 Octβ2R 中引入了 Y337F 突变。 Crispants 对咪丙环虫酯表现出超过三倍的抗性。总之，本研究鉴定并验证了一个新的咪丙环虫酯抗性突变。需要进一步研究以评估 Y337F 在当前治疗策略下与操作抗性相关的表型强度。
