The biological bases of wanting have been characterized in mammals, but whether an equivalent wanting system exists in insects remains unknown. In this study, we focused on honey bees, which perform intensive foraging activities to satisfy colony needs, and sought to determine whether foragers leave the hive driven by specific expectations about reward and whether they recollect these expectations during their waggle dances. We monitored foraging and dance behavior and simultaneously quantified and interfered with biogenic amine signaling in the bee brain. We show that a dopamine-dependent wanting system is activated transiently in the bee brain by increased appetite and individual recollection of profitable food sources, both en route to the goal and during waggle dances. Our results show that insects share with mammals common neural mechanisms for encoding wanting of stimuli with positive hedonic value.

The ethological study of dance behaviour has yielded some findings since Karl Von Frisch discovered and interpreted the ‘dance language’ in the honey bee. However, the function and role of long non-coding RNAs on dance behaviour are hardly known until now. In this study, the differential expression patterns of lncRNAs in the brains of waggling dancers and non-dancing bees were analysed by RNA sequencing. Furthermore, lncRNA-mRNA association analysis was constructed to decipher the waggle dance. The results of RNA sequencing indicated that a total of 2877 lncRNAs and 9647 mRNAs were detected from honey bee brains. Further comparison analysis displayed that two lncRNAs, MSTRG.6803.3 and XR_003305156.1, may be involved in the waggle dance. The lncRNA-mRNA association analysis showed that target genes of differentially expressed lncRNAs in the brains between waggling dancers and non-dancing bees were mainly annotated in biological processes related to metabolic process, signalling and response to stimulus and in molecular function associated with signal transducer activity, molecular transducer activity and binding. Nitrogen metabolism was likely implicated in the modulation of the waggle dance. Our findings contribute to further understanding the occurrence and development of waggle dance.

MicroRNAs (miRNAs) play a vital role in the nerve regulation of honey bees (Apis mellifera). This study aims to investigate the differences in expression of miRNAs in a honey bee’s brain for olfactory learning tasks and to explore their potential role in a honey bee’s olfactory learning and memory. In this study, 12 day old honey bees with strong and weak olfactory performances were utilized to investigate the influence of miRNAs on olfactory learning behavior. The honey bee brains were dissected, and a small RNA-seq technique was used for high-throughput sequencing. The data analysis of the miRNA sequences revealed that 14 differentially expressed miRNAs (DEmiRNAs) between the two groups, strong (S) and weak (W), for olfactory performance in honey bees were identified, which included seven up-regulated and seven down-regulated. The qPCR verification results of the 14 miRNAs showed that four miRNAs (miR-184-3p, miR-276-3p, miR-87-3p, and miR-124-3p) were significantly associated with olfactory learning and memory. The target genes of these DEmiRNAs were subjected to the GO database annotation and KEGG pathway enrichment analyses. The functional annotation and pathway analysis showed that the neuroactive ligand-receptor interaction pathway, oxidative phosphorylation, biosynthesis of amino acids, pentose phosphate pathway, carbon metabolism, and terpenoid backbone biosynthesis may be a great important pathway related to olfactory learning and memory in honey bees. Our findings together further explained the relationship between olfactory performance and the brain function of honey bees at the molecular level and provides a basis for further study on miRNAs related to olfactory learning and memory in honey bees.

Sacbrood virus (SBV) is a significant problem that impedes brood development in both eastern and western honeybees. Whole-genome sequencing has become an important tool in researching population genetic variations. Numerous studies have been conducted using multiple techniques to suppress SBV infection in honeybees, but the genetic markers and molecular mechanisms underlying SBV resistance have not been identified. To explore single nucleotide polymorphisms (SNPs), insertions, deletions (Indels), and genes at the DNA level related to SBV resistance, we conducted whole-genome resequencing on 90 Apis cerana cerana larvae raised in vitro and challenged with SBV. After filtering, a total of 337.47 gigabytes of clean data and 31,000,613 high-quality SNP loci were detected in three populations. We used ten databases to annotate 9359 predicted genes. By combining population differentiation index (F_ST) and nucleotide polymorphisms (π), we examined genome variants between resistant (R) and susceptible (S) larvae, focusing on site integrity (INT < 0.5) and minor allele frequency (MAF < 0.05). A selective sweep analysis with the top 1% and top 5% was used to identify significant regions. Two SNPs on the 15th chromosome with GenBank KZ288474.1_322717 (Guanine > Cytosine) and KZ288479.1_95621 (Cytosine > Thiamine) were found to be significantly associated with SBV resistance based on their associated allele frequencies after SNP validation. Each SNP was authenticated in 926 and 1022 samples, respectively. The enrichment and functional annotation pathways from significantly predicted genes to SBV resistance revealed immune response processes, signal transduction mechanisms, endocytosis, peroxisomes, phagosomes, and regulation of autophagy, which may be significant in SBV resistance. This study presents novel and useful SNP molecular markers that can be utilized as assisted molecular markers to select honeybees resistant to SBV for breeding and that can be used as a biocontrol technique to protect honeybees from SBV.

Compréhension de l'axe intestin-microbiote-cerveau : un modèle biologique pour analyser l'impact du microbiote sur l'apprentissage, la mémoire et le comportement défensif chez les abeilles domestiques: La compréhension de la façon dont les microbiotes influencent le comportement et les fonctions cognitives constitue un défi majeur en biologie moderne. Les abeilles mellifères offrent une opportunité unique pour étudier la relation entre les bactéries intestinales et le cerveau en raison de leur microbiote plus simple par rapport aux mammifères. Cette thèse de doctorat vise à découvrir l'axe cerveau-intestin chez les abeilles mellifères (Apis mellifera). La recherche sur les bourdons a montré que les bactéries Lactobacillus augmentent les niveaux d'acide lysophosphatidique (LPA) dans leur hémolymphe, améliorant la mémoire des indices visuels malgré l'absence de récepteurs LPA. Pour investiguer, nous avons étudié si les suppléments de LPA pourraient améliorer l'apprentissage et la mémoire des odeurs chez les abeilles mellifères et exploré les mécanismes sous-jacents. En utilisant le conditionnement différentiel du réflexe d'extension de la trompe (PER), nous avons constaté que le LPA améliorait l'apprentissage olfactif et la mémoire à long terme chez les abeilles mellifères. Cette amélioration pourrait impliquer le récepteur à la sérotonine 5-HT7, qui partage des similitudes avec les récepteurs LPA mammifères. Le blocage de ce récepteur a altéré l'apprentissage et la mémoire des abeilles non traitées et inversé les effets des suppléments de LPA, indiquant que le LPA influence la cognition via le récepteur 5-HT7. Nos résultats suggèrent que les métabolites bactériens tels que le LPA peuvent affecter la cognition des abeilles par des voies neurales non traditionnelles. Le LPA agit par le biais du récepteur à la sérotonine 5-HT7, ce qui soulève des questions sur son impact sur les réactions défensives étant donné l'association de la sérotonine avec la sensibilité au dard. Cependant, la stimulation du récepteur 5-HT7 n'a pas affecté la réponse des abeilles au sucrose, suggérant que d'autres neurotransmetteurs tels que l'octopamine et la dopamine pourraient influencer les comportements appétitifs. Pour étudier si les métabolites bactériens affectent la sensibilité au dard, nous avons étudié le comportement défensif des abeilles mellifères en utilisant le test de la réponse d'extension de l'aiguillon (SER). Les abeilles colonisées par différentes souches bactériennes ont montré des réponses variées aux chocs électriques, indiquant des effets potentiels sur la stimulation aversive. Cependant, la contamination dans nos groupes expérimentaux limite la preuve concluante, soulignant la nécessité de recherches supplémentaires.