In order to explore the impact of insect density on the edge effect of Bactrocera minax (Diptera: Tephritidae) adult distribution in orange orchards, traps were set up in orchards with maggot infestation rates of 2%, 4%, and 20% to attract adults. The study compared differences in distribution between the side with noncitrus trees and the side farther away from them. The results showed that at lower insect densities (2% and 4% maggot infestation rates), the proportion of insect trap sites and the number of insects per trap on the side of the orchard adjacent to the trees were significantly higher than that on the side away from the noncitrus trees, additionally, the proportion of adults captured 10 to 20 m away from the side of noncitrus trees was also significantly higher than at other distances. However, at higher insect density (20% maggot infestation rates), there were no significant differences in the proportion of insect traps or the number of insects per trap between the adjacent and distant sides of the trees. Similarly, there were no significant differences in the proportion of adults captured at distances of 10, 20, 30, and 40 m away from the side of noncitrus trees in the orchard. In summary, at low insect density, B. minax adults exhibit a strong edge effect, concentrating on the side of the orchard with noncitrus trees, whereas at high insect density, they are evenly distributed throughout the orchard.

Bactrocera tau is an economically important invasive pest damaging many vegetables and fruits. Due to the hidden characteristics of its larval infestation, a strategy for regulating B. tau adults' olfactory-driven behaviors to control the pest is desirable. The olfactory co-receptor (Orco) is a key chemosensory membrane protein in insect olfactory systems. However, the function of Orco in the olfactory-driven behaviors of this pest remains under explored. In this study, we characterized the Orco gene from B. tau, named BtauOrco. The complete open reading frame (ORF) of BtauOrco is 1422 bp, which encodes a protein of 473 amino acids, with seven structural domains in the transmembrane, and shares high identity with other insect Orcos. Real-time quantitative PCR (RT-qPCR) analysis showed that BtauOrco is predominantly expressed in the antennae of both male and female B. tau flies. After silencing Orco in B. tau flies, we found the responses of Orco-silenced flies to nine behaviorally active compounds were abolished. Moreover, the Orco-silenced flies exhibited an impaired foraging behavior. Our findings suggested that Orco plays a crucial role in B. tau olfactory-driven behaviors, which indicates that Orco is an excellent target for the control of B. tau.

Uridine diphosphate (UDP)-glycosyltransferases are essential phase-II detoxification enzymes that glycosylate lipophilic endogenous and xenobiotic compounds and they are thought to play a role in driving the evolution of insecticide resistance. To examine if the resistance to thiamethoxam and imidacloprid was associated with enhancement of UDP-glycosyltransferase in the whitefly, Bemisia tabaci, we first conducted UDP enzyme activity assays in resistant and sensitive strains in the absence and presence of UGT inhibitors. We found that the UGT enzyme content of resistant whitefly was significantly 5.02- to 10.69-fold higher than that of sensitive whitefly. Individual UGT inhibitors effectively inhibited UGT activity in resistant strains and their effect was synergistic when applied in combination. We then used bioinformatic, molecular, genetic and in silico approaches to determine if UGT352A3 encoded a key enzyme linked to neonicotinoid resistance. In resistant strains, UGT352A3 expression was elevated 1.8- to 6.6-fold compared to susceptible strains, which correlated with higher resistance ratios. RNAi-mediated knockdown of UGT352A3 in resistant whitefly strains significantly heightened their sensitivity to the insecticides, thiamethoxam and imidacloprid. Molecular docking analyses further confirmed a strong binding affinity between UGT352A3 and thiamethoxam and imidacloprid, which supported a role in their metabolism. These findings suggest that UGT352A3 is a critical factor in the development of resistance to thiamethoxam and imidacloprid in whitefly, underscoring its important potential as a new pest resistance management target.

Accurate field pest counting is crucial for timely reporting, rational pesticide use, and effective pest control. However, existing methods struggle with precisely detecting andcounting the tiny pests in field conditions due to two challenges: (I) environmental complexity and the minimal distinctive features of pests, which lead to high False Negative (FN) and False Positive (FP) rates; and (II) the inability to correct detection errors through secondary optimization. We propose the Prompt-Guided Pest Counter (PGPC), a method using visual prompts to improve detection and counting. Firstly, PGPC employs a fully convolutional encoder-decoder architecture with Patch Self Attention (PSA) to enhance feature extraction capability. It is trained using Object Counting Loss (OC Loss) to enable precise detection and counting by predicting the location of each pest. Secondly, we introduce a visual prompt-based FN-FP prototype matching branch to address detection errors. This branch uses a small number of prompt boxes to extract features and generates response maps, which are then fused with original features via an Adaptive Feature Gate (AFG) to perform secondary optimization on erroneous results. We collected a large-scale rice planthopper dataset from 2023 to 2024, containing over 250,000 annotations, and categorized into low-, medium-, and high-densities based on pest counts. Detection accuracy and counting errors were employed as evaluation metrics. The results demonstrate that visual prompts can optimize detection in complex environments, improving the model’s F1-score by 2.11% and reducing RMSE by 22.4% and 22.6% for medium- and high-densities, respectively. Ultimately, PGPC achieves an F1-score of 88.52%, with RMSE of 2.08, 5.97, and 10.81 for low-, medium-, and high-densities. Compared to state-of-the-art methods, PGPC maintains lower computational overhead while delivering competitive detection and counting performance.

In practice, acquiring and annotating data in specialized domains can be costly, thereby constraining the performance and applicability of deep learning. Utilizing generative models to synthesize data proves to be an effective augmentation technique. Therefore, this research proposes a diseased leaf generation pipeline to diversify the maize disease datasets. We introduce the Dual-Perception Cycle-Consistent Generative Adversarial Network (DP-CycleGAN). During training, incorporating our proposed Structure Perception (SP) loss and Texture Perception (TP) loss functions. These losses guide the model 's attention areas through activation reconstruction and mask mechanisms, thereby improving the overall perceptual quality of the generated images and the realism of the disease lesions. We constructed a maize leaf mixed disease dataset to simulate the complex conditions of real-world disease occurrence. Experimental results show that the DP-CycleGAN generates higher-quality and more realistic diseased leaf images. Compared to CycleGAN and state-of-the-art method, DP-CycleGAN shows a 29.6% and 15.7% reduction in Fre chet Inception Distance (FID) scores and a 125.3% and 61.5% increase in Structural Similarity (SSIM) values, respectively. Simultaneously, by incorporating synthetic data during training, our approach significantly enhances the performance of the recognition model in scenarios of both data abundance and scarcity, with improvement rates exceeding two times those of existing state-of-the-art methods. This contributes to the application of Artificial Intelligence (AI) in agricultural production practices.

Trade- offs between evolutionary gain and loss are prevalent in nature, yet their genetic basis is not well resolved. The evolution of insect resistance to insecticide is often associated with strong fitness costs; however, how the fitness trade- offs operates remains poorly understood. Here, we show that the mitogen- activated protein kinase (MAPK) pathway and its upstream and downstream actors underlie the fitness trade- offs associated with insecticide resistance in the whitefly Bemisia tabaci . Specifically, we find a key cytochrome P450 gene CYP6CM1 , that confers neonicotinoids resistance to in B. tabaci , is regulated by the MAPKs p38 and ERK through their activation of the transcription factor cAMP- response element binding protein. However, phosphorylation of p38 and ERK also leads to the activation of the transcription repressor Cap "n" collar isoform C (CncC) that negatively regulates exuperantia (Ex), vasa (Va), and benign gonial cell neoplasm (Bg ), key genes involved in oogenesis, leading to abnormal ovary growth and a reduction in female fecundity. We further demonstrate that the transmembrane G protein- coupled receptor (GPCR) neuropeptide FF receptor 2 (NPFF2) triggers the p38 and ERK pathways via phosphorylation. Additionally, a positive feedback loop between p38 and NPFF2 leads to the continuous activation of the MAPK pathways, thereby constitutively promoting neonicotinoids resistance but with a significant reproductive cost. Collectively, these findings provide fundamental insights into the role of cis- trans regulatory networks incurred by GPCR-MAPK signaling pathways in evolutionary trade- offs and applied knowledge that can inform the development of strategies for the sustainable pest control.

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 BTβ1A58T&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.

Bactrocera minax is a disastrous pest of citrus crops in China. Numerous studies focused on the molecular mechanism of odorant perception of B. minax, but the molecular mechanism of odorant degradation remains unclear. Glutathione S-transferases (GSTs) are considered as a class of odorant-degrading enzymes involved in degrading odorant molecules in insects' olfactory system. Here, we identified a delta-class GST gene, BminGSTd3, from B. minax. It was predominantly expressed in adult's olfactory organ antennae. The bacterially expressed recombinant BminGSTd3 was able to catalyze the conjugation of glutathione (GSH) with 2, 4-dinitrochlorobenzene (CDNB). Spectrophotometric analysis showed that undecanol can inhibit catalytic activities of BminGSTd3. Metabolic assays exhibited that undecanol can be depleted by BminGSTd3. Undecanol is believed to be an important B. minax sex pheromone component. The other components of the pheromone remain unclear. To understand how BminGSTd3 specifically recognizes undecanol, a 3D model of BminGSTd3 was constructed by homology modeling. Molecular docking based on this model revealed that E64 and S65 are the key amino acids recognizing undecanol, and this was proven by site-directed mutagenesis and intrinsic fluorescence assays. We suggest that BminGSTd3 is an undecanol metabolizing GST in B.minax, and E64 and S65 may serve as the key binding sites.

Rice planthoppers are among the most severe migratory pests affecting rice, characterized by small size and rapid reproduction, leading to sudden and explosive outbreaks. Therefore, timely and accurate monitoring of rice planthopper populations is crucial. Applying machine vision to field monitoring of rice planthoppers can reduce labor and material costs. Existing literature lacks research on field detection and counting of rice planthoppers, and general detection and counting methods suffer from performance degradation in complex environments. In this study, we propose the Rice Planthopper Counter (RPH-Counter), a novel detection and counting architecture. The model is a simple Fully Convolutional Network (FCN). Initially, we propose the Object Counting loss (OC loss), which includes four sub-loss functions that compel the FCN to learn each object's center and boundary positions while constraining false positives. After training, the FCN can predict a separate spot for each rice planthopper, achieving precise localization and counting of the pests. Then, we propose the Self-Attention Feature Pyramid Network (SAFPN) by adding additional Spatial Self-Attention (SSA) modules at the lateral connections of C3 to C5, enhancing the model's performance in complex environments at a lower computational cost. We collected a large-scale field rice planthopper dataset, containing approximately 140,000 annotated rice planthoppers. The evaluation metrics are localization accuracy and counting error. Experimental results show that the RPH-Counter, with lower computational complexity, significantly improves performance, achieving an F1 score of 92.36%, a Mean Absolute Error (MAE) of only 2.40, and an R-squared (R2) of 0.985. Compared to the state-of-the-art object detectors, the F1 score improved by 8.62%, and the counting error decreased by 61%. Compared to the state-of-the-art density estimation methods, the counting error decreased by 23%, with precise localization ability and multi-class expandability. This method offers a new research approach and promising direction for field pest counting and pest population monitoring.

柑橘大实蝇Bactrocera minax(Enderlein),是柑橘的重要害虫.本文基于光学显微镜、扫描电镜、石蜡切片和透射电镜观察,对柑橘大实蝇的产卵器形态结构进行研究.结果表明,柑橘大实蝇产卵器由产卵器基节、翻缩膜和产卵针3部分组成,翻缩膜是浅黄色的柔软的细长管状结构,又分为骨化带、骨化环和膜质部3部分.骨化带表面有4条褐色的、纵向的、柔软的离散带.骨化环和膜质部表面存在小齿和无齿两种角质化鳞片,鳞片的一端与表皮连接,另外一端处于自由状态,鳞片以覆瓦状包围在骨化环和膜质部表面.骨化带和骨化环弯曲程度极低,而膜质部弯曲程度较大.产卵针由1块背片和2块腹片组成,2块腹片之间、背片与腹片之间与可折叠弯曲的柔性角质层连接.其背片两内侧均存在1个未封闭的圆环,其内部有肌肉(背腹肌)、气管、输卵管和直肠等组织或器官.产卵器上有毛形、腔锥形和钟形3种类型感受器.在产卵器收缩时,首先产卵针折叠在翻缩膜内,然后再一起折叠在基节内.因此,在成虫休息时,产卵器形成了产卵针(内层)、翻缩膜(中间层)和基节(外层)3个腹节的套叠.柑橘大实蝇的产卵器是伪产卵器,其结构或组织经过进化,从而适应其伪产卵器的外翻、弯曲、收缩折叠运动机制.本研究为理解昆虫进化和多样性,以及昆虫的产卵、交配和代谢物排泄等行为机制提供新的例证.

[目的]针对柑橘大实蝇Bactrocera mninax的特殊巡回扩散模式,通过研究不同日龄成虫(特定扩散阶段成虫)对蔗糖和蛋白的营养需求以及其精巢、卵巢发育进度和特定扩散阶段的交配产卵动态,明确柑橘大实蝇不同扩散阶段演替的营养基础与生殖发育节点,初步明晰其巡回扩散机制,为柑橘大实蝇成虫精准防控提供依据.[方法]测定各扩散阶段柑橘大实蝇雌雄成虫对蔗糖和蔗糖+酵母混合食物(蔗糖∶酵母=3∶1,m/m)(酵母的主要成分是蛋白质和维生素)的取食量,测定不同扩散阶段成虫对糖和蛋白的需求;解剖成虫卵巢和精巢;观察成虫交配产卵动态;分析其启动扩散的发育基础和节点.[结果]柑橘大实蝇外迁期(1日龄)和返迁前期(15日龄)雌成虫较其他扩散阶段雌成虫对蔗糖有显著高的取食量,外滞期(10日龄)雌成虫则对糖的取食量最小;迁动状态下,雄成虫对蔗糖的取食量显著低于雌成虫.柑橘大实蝇10日龄雌成虫的酵母摄入量最高,雄成虫则在1,10和30日龄对酵母摄入量高于15和20日龄雄成虫.10日龄雌成虫、10日龄雄成虫、20日龄雄成虫和30日龄雄成虫对蔗糖+酵母混合食物的取食量显著高于对单一蔗糖的取食量;1,15和20日龄雌成虫对蔗糖+酵母混合食物的取食量显著低于对单一蔗糖的取食量,而各日龄雄成虫对蔗糖+酵母混合食物的取食量与对单一蔗糖的取食量相比均未显著下降.添加酵母后,1,15,20和30日龄雌成虫及15日龄雄成虫对混合食物中蔗糖的摄取量较对单一蔗糖的摄取量显著降低.柑橘大实蝇雌成虫3级卵巢占比16％,50％和84％分别为羽化后第9.17,14.80和20.34天.5日龄雄成虫精巢体积最小,10日龄时开始显著增大,30日龄时精巢体积最大;10-20日龄雄成虫精巢长度则随日龄增大而增加,30日龄时有明显缩短.精巢宽度随日龄间断性突增,其中10和30日龄时较大.成虫交配始盛期(累积交配率为16％)、高峰期(累积交配率为50％)和盛末期(累积交配率为84％)分别为羽化后第16.90,22.06和27.42天;雌成虫产卵始盛期(累积产卵率16％)、高峰期(累积产卵率50％)和盛末期(累积产卵率84％)分别为羽化后第16.03,28.08和38.69天.[结论]外迁期和返迁前期柑橘大实蝇雌成虫对蔗糖有高需求;且迁动状态下(外迁期、返迁期和交互扩散期)的雌成虫相较雄成虫需求更强,即蔗糖为迁动必要营养.柑橘大实蝇在外滞期对蛋白摄取量最高,与卵巢发育始盛期吻合;雄成虫对蛋白的需求程度与其精巢体积大小相对应,蛋白与成虫生殖系统发育密切相关,可为其返迁扩散提供营养基础.成虫返迁前期与雌成虫卵巢发育高峰期和成虫交配始盛期相吻合.即成虫生殖系统发育状态与其启动返园扩散的时间节点密切相关,雌成虫卵巢发育成熟是其群体返园的决定性生理基础,可通过监测雌成虫卵巢发育进度对柑橘大实蝇返园扩散期进行预测.

The whitefly, Bemisia tabaci, comes up high metabolic resistance to most neonicotinoids in long-term evolution, which is the key problem of pest control. UGT glycosyltransferase, as a secondary detoxification enzyme, plays an indispensable role in detoxification metabolism. In this study, UGT inhibitors, 5-nitrouracil and sulfinpyrazone, dramatically augmented the toxic damage of neonicotinoids to B. tabaci. A UGT named UGT353G2 was identified in whitefly, which was notably up-regulated in resistant strain (3.92 folds), and could be induced by most neonicotinoids. Additionally, the using of RNA interference (RNAi) suppresses UGT353G2 substantially increased sensitivity to neonicotinoids in resistant strain. Our results support that UGT353G2 may be involved in the neonicotinoids resistance of whitefly. These findings will help further verify the functional role of UGTs in neonicotinoid resistance.

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.

[目的]柑橘大实蝇是一种严重为害柑橘类果实的经济害虫.研究其精巢、精泵以及精泵内骨骼生长发育状况,有助于提高柑橘大实蝇人工繁殖效率以及其田间防治效果,为柑橘大实蝇的预测预报及防治提供理论基础.[方法]基于光学显微镜测量恒温和室温条件下柑橘大实蝇雄虫的精巢、精泵以及精泵内骨骼的长度和宽度,并建立其长度、宽度和指数的函数模型,比较恒温和室温 2 种饲养条件下其雄虫器官发育状况差异.[结果]无论是在恒温还是室温条件下饲养,随着柑橘大实蝇雄成虫日龄的增加,其精巢、精泵以及精泵内骨骼的长度、宽度和指数变化趋势均符合幂函数增长模型.在恒温和室温条件下,其雄虫的精巢宽度、精泵的长度和宽度以及指数、精泵内骨骼宽度均无明显差异.在室温条件下饲养的雄虫的精巢长度[(4.00±0.14)mm]及指数(3.40±0.14)、精泵内骨骼长度[(1.65±0.03)mm]及指数(1.84±0.08)均分别显著高于在恒温条件下饲养的雄虫的精巢长度[(3.75±0.13)mm]及指数(3.19±0.14)、精泵内骨骼长度[(1.61±0.03)mm]及指数(1.77±0.08).[结论]变温(室温)比恒温更有利于柑橘大实蝇雄虫的精巢和精泵内骨骼的发育,并推荐使用精泵长度推断其雄虫日龄的方法.

针对当前玉米病害发生量大、病情复杂、难以防治,严重影响玉米产量和质量的问题,提出了一种基于卷积神经网络和迁移学习的玉米叶片病害检测与识别方法.首先收集了 3 827张玉米健康叶片图像和3种不同的玉米病害叶片图像样本,为了使模型拥有更好的泛化能力,使用生成对抗网络对样本进行处理,得到分辨率更高的样本,再对样本进行平移旋转,使样本数量达到5 153张.然后构建ResNet模型,分别对ResNet34、ResNet50及对其添加CBAM注意力机制和FPN特征金字塔网络,并通过迁移学习方法将预训练权重迁移到训练模型中.试验结果表明,ResNet50结合CBAM注意力机制模型的准确率达到了 97.5％,相比ResNet50模型准确率提升了 4.2百分点,相比ResNet34模型准确率提升了 4.9百分点.本研究表明,提出的ResNet50结合CBAM注意力机制模型能够较精准地检测识别玉米枯萎叶、锈病叶、灰斑病叶和健康叶.并可将模型安装在无人机等移动设备上,实现对玉米叶片病害智能化防治,而且后期还会扩充更多的植物病害数据,实现对多类植物病害的检测,为智慧农业添砖加瓦,促进农业防治现代化.

The sweet potato whitefly, Bemisia tabaci, (Gennadius) (Hemiptera:Aleyrodidae) is a global pest of crops. Neonicotinoids are efficient insecticides used for control of this pest. Insecticidal targets of neonicotinoids are insect nicotinic acetylcholine receptors (nAChRs). Here, we characterized and cloned the full length of the nAChR β1 subunit (BTβ1) in B. tabaci and confirmed the consistency of BTβ1 in B. tabaci MEAM1 and MED. Expression levels of BTβ1 in different developmental stages and body parts of adults were investigated and compared in B. tabaci MED. dsRNA was prepared to knock down BTβ1 in adult B. tabaci and significantly decreases the susceptibility to five neonicotinoid insecticides, including imidacloprid, clothianidin, thiacloprid, nitenpyram, and dinotefuran. This study indicated BTβ1 as a notable site influencing the susceptibility of B. tabaci to neonicotinoids.

Thermal stress usually leads to excessive production of reactive oxygen species (ROS) in all aerobic organisms. Catalases (CAT) are the key antioxidant enzymes, which act as the first line of defense against ROS in the antioxidant pathway. The highly invasive and widely distributed whitefly Bemisia tabaci MED damages plants by feeding as well as by transmitting many plant viruses. Previous studies have shown that strong adaptability to high temperature helps explain the spread of MED around the world. However, the mechanism underlying high temperature adaptation of this pest is not well understood. In this study, 6 CAT genes were identified from the MED genome and transcriptome dataset, among which BtCAT1, BtCAT2, and BtCAT3 were found to be highly expressed in adults. The expression of BtCAT1, BtCAT2, or BtCAT3 increased with induction temperature and induction time. The MED was exposed with mean high temperature (30 °C or 35 °C) and a short‐term extremely high temperature (39 °C or 41 °C) after the silencing of BtCAT1, BtCAT2, or BtCAT3 to significantly increased ROS levels by at least 0.5 times and significantly decreased survival rate and fecundity of MED adults. The ROS level in the treated specimens gradually returned to a normal level after 24 h at 25 °C, but the survival rate still declined significantly. Taken together, our results demonstrate that CAT could help B. tabaci adapt to long‐term mean high temperatures and short‐term extremely high temperatures by eliminating excessive ROS.

【Objective】To explore the recognition mechanisms of Bmin OBP6 and its ligands,a C terminus-truncated Bmin OBP6（TOBP6） was constructed in this study.Subsequently,the binding affinities of TOBP6 and the wild type protein Bmin OBP6 to1-undecanol and （+）-limonene under different pH conditions were determined.【Method】3D structure of BminOBP6 was built by homology modeling through the online software SWISS MODEL.Based on the established BminOBP6 3D model,the C terminus sequence after sixth α-helix of BminOBP6 was determined.This C terminus sequence is the sequence that will be removed from Bmin OBP6 in the subsequent study.Specific primers were designed to amplify the encoding sequence of BminOBP6 C terminustruncated mutant TOBP6.Then the recombinant expression vector pET-32a/TOBP6 was constructed.Recombinant expression vectors pET-32a/TOBP6 and pET32a/BminOBP6 that has been made before in our lab were transformed into Escherichia coli cells BL21 （DE3） to express the TOBP6 and BminOBP6 recombinant proteins,respectively.Fluorescence competitive binding assays were conducted to determine the binding affinities of TOBP6 and BminOBP6 to 1-undecanol and （+）-limonene under different pH（7.4 and 5.0） conditions.【Result】Amino acid sequence alignments revealed that BminOBP6 shared 62.6%identity with Culex quinquefasciatus Cqui OBP1,and thus the 3D structure of Cqui OBP1 was used as the template in the homology modeling of BminOBP6.The 3D structure of BminOBP6 indicated that the C terminus sequence after α6 of BminOBP6 is a sequence of 8 amino acid residues （D117-P124）.Based on this result,the encoding sequence of TOBP6 was cloned and its recombinant expression vector pET-32a/TOBP6 was built.Recombinant expression vectors pET-32a/TOBP6 and pET32a/BminOBP6 were then transformed into E.coli cells BL21 （DE3） to express the TOBP6 and BminOBP6 recombinant proteins,respectively.The fluorescence competitive binding results showed that the binding affinity of BminOBP6 to 1-undecanol and （+）-limonene was quite strong at pH 7.4,the K i values were 6.89 and 9.50μmol·L -1 ,respectively.However,when the pH decreased to 5.0,BminOBP6 completely lost its binding capacity to 1-undecanol and exhibited an obvious decrease in binding to （+）-limonene (the K i value increased from 9.50μmol·L -1 to31.26μmol·L -1 ).The binding affinity of TOBP6 to 1-undecanol and （+）-limonene was completely abolished regardless of p H conditions.【Conclusion】Changes in pH have a significant effect on the ligand binding and release of BminOBP6,and the C terminus of BminOBP6 is crucial for BminOBP6 to bind its ligands.

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 (Ki = 19.57 ± 0.45) compared with that of the wild-type protein BminOBP3 (Ki = 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.

Chinese citrus fly, Bactrocera minax (Enderlein; Diptera: Tephritidae), which attacks citrus fruits in China is one of the most important international quarantine pests.Understanding the function of visual organs is the basis of trapping and prevention for management of pests such as B. minax.In this study, take-off ability and crawling experiments were conducted using 5 groups of B. minax all with different visual blinding treatments (blind ocelli, blind left compound eye, blind right compound eye, blind compound eyes, blind ocelli and compound eyes) and a corresponding control that was not blinded.We found that both the left and right compound eyes played a critical role in the vertical and horizontal crawling behavior of B. minax, while the ocelli did not.However, the perception of ambient light by ocelli or either compound eye had a significant influence on take-off of B. minax.Elucidating the monocular and compound eye functions of B. minax will help us to develop better visual traps for this important pest of citrus.