Neonicotinoid insecticides, which target insect nicotinic acetylcholine receptors (nAChRs), have been widely and intensively used to control the whitefly, Bemisia tabaci, a highly damaging, globally distributed, crop pest. This has inevitably led to the emergence of populations with resistance to neonicotinoids. However, to date, there have been no reports of target-site resistance involving mutation of B. tabaci nAChR genes. Here we characterize the nAChR subunit gene family of B. tabaci and identify dual mutations (A58T&R79E) in one of these genes (BTβ1) that confer resistance to multiple neonicotinoids. Transgenic D. melanogaster, where the native nAChR Dβ1 was replaced with BTβ1^A58T&R79E, were significantly more resistant to neonicotinoids than flies where Dβ1 were replaced with the wildtype BTβ1 sequence, demonstrating the causal role of the mutations in resistance. The two mutations identified in this study replace two amino acids that are highly conserved in >200 insect species. Three-dimensional modelling suggests a molecular mechanism for this resistance, whereby A58T forms a hydrogen bond with the R79E side chain, which positions its negatively-charged carboxylate group to electrostatically repulse a neonicotinoid at the orthosteric site. Together these findings describe the first case of target-site resistance to neonicotinoids in B. tabaci and provide insight into the molecular determinants of neonicotinoid binding and selectivity.

Insect odorant-binding proteins (OBPs) are significant in binding and transporting odorants to specific receptors. Our previous study demonstrated that BminOBP3 exhibited a strong affinity with undecanol. However, the binding mechanism between them remains unknown. Here, using homology modeling and molecular docking, we found that the C-terminus (I116-P122), especially the hydrogenbonds formed by the last three amino acid residues (V120, F121, and P122) of the C-terminus, is essential for BminOBP3′s ligand binding. Mutant binding assays showed that the mutant T-OBP3 that lacks C-terminus (I116-P122) displayed a significant decrease in affinity to undecanol (K_i = 19.57 ± 0.45) compared with that of the wild-type protein BminOBP3 (K_i = 11.59 ± 0.51). In the mutant 3D2a that lacks F121 and P122 and the mutant V120A in which V120 was replaced by alanine, the bindings to undecanol were completely abolished. In conclusion, the C-terminus plays a crucial role in the binding interactions between BminOBP3 and undecanol. Based on the results, we discussed the ligand-binding process of BminOBP3.

Pest management has long been a critical aspect of crop protection. Insect behavior is of great research value as an important indicator for assessing insect characteristics. Currently, insect behavior research is increasingly based on the quantification of behavior. Traditional manual observation and analysis methods can no longer meet the requirements of data volume and observation time. In this paper, we propose a method based on region localization combined with an improved 3D convolutional neural network for six grooming behaviors of Bactrocera minax: head grooming, foreleg grooming, fore-mid leg grooming, mid-hind leg grooming, hind leg grooming, and wing grooming. The overall recognition accuracy reached 93.46%. We compared the results obtained from the detection model with manual observations; the average difference was about 12%. This shows that the model reached a level close to manual observation. Additionally, recognition time using this method is only one-third of that required for manual observation, making it suitable for real-time detection needs. Experimental data demonstrate that this method effectively eliminates the interference caused by the walking behavior of Bactrocera minax, enabling efficient and automated detection of grooming behavior. Consequently, it offers a convenient means of studying pest characteristics in the field of crop protection.

Insects perceive external light signals through their visual organs, which they use to search for food, avoid enemies, pursue mates, and even escape from predators (Vogt & Desplan 2007; Yang & Yeo 2019). The visual organs of insects mainly include compound eyes, dorsal monocular eyes, and lateral monocular eyes (Gillott 2005; González-Martín-Moro et al. 2017). In the case of complete absence of chemical odor, some insects can identify and locate their hosts by relying on vision (Stenberg & Ericson 2007; Reeves & Lorch 2009; Muijres et al. 2014). Many herbivorous insects express a color preference that helps them find optimal oviposition substrates (Prokopy & Owens 1983; Scherer & Kolb 1987; Ogawa et al. 2013). It is striking that the function of the visual system in many groups has not been investigated at all, and for many families only 1 species has been studied to date (n = 46 families, 55%) (Casper et al. 2021). Many groups of insects are understudied, including numerous early-diverging taxa, e.g., Hemiptera, Thysanoptera, and most fly families (Heath et al. 2020; An et al. 2018; Hannah et al. 2019).