Differences in ASP1 expression and binding dynamics to queen mandibular pheromone HOB between Apis mellifera and Apis cerana workers reveal olfactory adaptation to colony organization.

The eastern Apis cerana (Ac) and the western Apis mellifera (Am) are two closely related and most economically valuable honeybee species managed extensively worldwide. However, how worker bees of Ac and Am are adapted to their colony organization remains to be uncovered. Here, we found that the expression level of gene encoding antennae-specific proteins 1 (ASP1, a key regulator in recognizing queen mandibular pheromone) was positively correlated with the colony sizes in both bee species, and the expression level in Am was higher than that in Ac , suggesting that ASP1 may play an important role in maintaining colony homeostasis. Using competitive binding assay, molecular docking, and site-directed mutagenesis, we then confirmed the good binding affinities of both Ac-ASP1 and Am-ASP1 to methyl p-hydroxy benzoate (HOB), and Val115 was the key amino acid. However, the affinity of Am-ASP1 was stronger than that of Ac-ASP1. EAG analysis further demonstrated that antennae of Am worker bees had faster depolarization and repolarization in response to HOB stimulation. Taken together, these findings indicate that the differences in expression levels and binding dynamics allow ASP1 recognizing HOB to potentially serve as a specific regulator of colony organization in Ac and Am. [ABSTRACT FROM AUTHOR]