Dorsal transcription factor and the neural regulation of aggressive behavior in Apis mellifera

• Grant number: 25/04302-9
• Support Opportunities: Scholarships abroad - Research Internship - Doctorate
• Start date: September 19, 2025
• End date: September 18, 2026
• Field of knowledge: Biological Sciences - Genetics - Animal Genetics
• Principal Investigator: Klaus Hartmann Hartfelder
• Grantee: Leonardo Campana
• Supervisor: Martin Giurfa
• Host Institution: Faculdade de Medicina de Ribeirão Preto (FMRP). Universidade de São Paulo (USP). Ribeirão Preto , SP, Brazil
• Institution abroad: Institut De Biologie Paris-Seine, France
• Associated to the scholarship: 23/13713-7 - Beyond immunity: The role of innate immune signaling pathways in the defensive behavior of highly eusocial bees, BP.DR

Abstract

The behavior of social organisms can be studied at both individual and collective levels. In many cases, an individual's behavioral tendency predicts that of the group, as social signals modulate the flexible expression of genetically inherited behaviors. The honey bee (Apis mellifera) exemplifies this phenomenon, displaying collective behaviors influenced by social cues and genetic inheritance. Within the colony, workers perform various tasks, including defense, which is carried out by guard bees. These bees coordinate attacks against threats through pheromonal signals, such as isoamyl acetate (IAA), which is detected by the antennae and processed in brain structures like the antennal lobes and mushroom bodies. Aggressiveness in bees is associated with changes in the levels of biogenic amines, such as serotonin and dopamine, which modulate behavior. Additionally, pheromones and odors can alter gene expression in the brain, affecting immediate early genes (IEGs) and transcription factors like NF-¿B (Dorsal in insects), which are involved in neural and immune processes. Recent studies suggest that, beyond its classical role in immunity, Dorsal may regulate aggressive behaviors. In this context, the present project aims to investigate how the pharmacological inhibition of Dorsal affects the perception of alarm pheromones and synaptic plasticity in A. mellifera workers, comparing winter and summer bees, which exhibit physiological and behavioral differences. The study will be conducted at the Institut de Biologie Paris-Seine, using bees from the university's apiary. Two experimental groups will be established: a control group, fed with a 50% honey solution, and a treated group, receiving the same solution containing PDTC, a Dorsal inhibitor. The experiment will be repeated in winter (October 2025) and summer (April 2026) to compare seasonal responses. The groups will undergo calcium imaging. Anesthetized bees will have their antennal lobes exposed and receive olfactory stimuli of IAA (alarm pheromone) and geraniol (control). Neuronal activity will be recorded and analyzed to map glomerular activation and assess Dorsal's role in alarm pheromone processing. To investigate synaptic plasticity, brains of treated and untreated bees will be dissected, fixed, sectioned, and stained with anti-synapsin and phalloidin antibodies to mark synapses and actin, respectively. Images obtained through confocal microscopy will be processed for 3D reconstruction and quantification of microglomeruli. This study seeks to elucidate the neural and molecular mechanisms by which Dorsal regulates aggression in bees, focusing on pheromone perception and synaptic plasticity. By comparing bees from different seasons, it will contribute to the understanding of seasonal adaptations in social organisms and the evolution of defensive behavior in eusocial insects. Furthermore, investigating Dorsal's non-canonical function in the brain may provide new insights into the interaction between immunity and aggressive behavior, with implications for other organisms and the neurobiology of social behavior.