Neuromodulation of Behavioral Specialization: Tachykinin Signaling Inhibits Task-specific Behavioral Responsiveness in Honeybee Workers

Abstract

Behavioral specialization is key to the success of social insects and often compartmentalized among colony members leading to division of labor. Response thresholds to task-specific stimuli proximally regulate behavioral specialization but their neurobiological regulation is not understood. Here, we show that response thresholds to task-relevant stimuli correspond to the specialization of three behavioral phenotypes of honeybee workers. Quantitative neuropeptidome comparisons suggest two tachykinin-related peptides (TRP2 and TRP3) as candidates for the modification of these response thresholds. Based on our characterization of their receptor binding and downstream signaling, we then confirm the functional role of tachykinins: TRP2 injection and RNAi cause consistent, opposite effects on responsiveness to task-specific stimuli of each behaviorally specialized phenotype but not to stimuli that are unrelated to their tasks. Thus, our study demonstrates that TRP-signaling regulates the degree of task-specific responsiveness of specialized honeybee workers and may control the context-specificity of behavior in animals more generally.

Neuropeptides as potential modulators of behavioral transitions in the ant Cataglyphis nodus

“…This is different in the honeybee, where TK brain expression is upregulated in foragers (Han et al, 2021; Takeuchi et al, 2003). Manipulation experiments further indicate that TK modulates response thresholds of the proboscis extension response (PER) in a stage specific manner: Whereas TK injection decreased PER responsiveness, TK knockdown had an opposite effect (Han et al, 2021). Injection of TK and Ast‐A in another study induced aggressive behavior in 7‐day‐old honeybee workers (Pratavieira et al, 2018).…”

“…They are involved in physiological and developmental processes and in the modulation of many essential behaviors (for reviews, see Fricker, 2012; Kastin, 2013; Nässel & Zandawala, 2019). Recent studies suggest that the neuropeptides allatostatin‐A (Ast‐A), tachykinin (TK), and corazonin (Crz) act as regulators of behavioral plasticity in social insects (Gospocic et al, 2017; Han et al, 2021; Pratavieira et al, 2014; Schmitt et al, 2017; Takeuchi et al, 2003). Age‐related fluctuations of Ast‐A and/or TK have been revealed in honeybees (Pratavieira et al, 2014; Takeuchi et al, 2003) and in the ant Cataglyphis fortis (Schmitt et al, 2017).…”