Identification and characterization of sugar receptors in the western honey bee,Apis mellifera

Abstract

The sense of taste gives animals precious information about the quality and nutritional value of food. In honey bee, taste is vital for choosing beneficial food sources, water, resins, and for nest mate identification. Although sugar detection is a crucial factor in determining the acceptability of nectar and pollen collection in the honey bee, little is known about the molecular and neural correlates underlying sugar perception in honey bees. Here we functionally identified a sugar receptor of the western honey bee, Apis mellifera, which were most related phylogenetically with sugar receptors of Drosophila melanogaster such as DmGr64a-f, Gr61a, and Gr5a. We characterized that gustatory receptor 1 of A. mellifera (AmGr1) responded to sucrose, glucose, trehalose, and maltose with a dose-dependent manner. Notably, we firstly found that the expression patterns of AmGr1 and AmGr2 is distinct from those in Drosophila. AmGr1 alone showed fully functional, but showed different sensitivity from a heterodimer of AmGr1 and AmGr2. That is, co-expression of AmGr1 and AmGr2 demonstrated higher sensitivity to glucose, while lower sensitivity to sucrose, trehalose, and maltose, compared to AmGr1 expression alone. Expression patterns in the antenna of honey bees showed that AmGr1 and AmGr2 were co-localized in the antennal neurons or not, and especially AmGr1 were highly expressed at the distal segment of the antennae. Our study suggests that sugar receptors of the honey bee function as heterodimers (or monomer or mono-dimer), indicating that AmGr2 is required for providing honeybees with variability of sugar perceptions. This functional organization of the sugar receptor of the honey bee strongly indicates the correlation of internal and external sensing of sugars.