Aquaporins in the honeybee crop--a new function for an old organ.

Nectar used by bees as a food source is collected and stored in the crop, where it is transported and converted into honey. The production of honey involves water uptake from nectar. However, the crop is a portion of the insect foregut that has been characterized solely as a food storage organ. Aquaporins are integral membrane proteins that function as specific canal for water transport and are abundant in tissues with high water permeability. In this study, we detected five predicted genes for aquaporins in the gut of the honeybee Apis mellifera. We evaluated the aquaporins' localization in the crop by using an anti-aquaporin antibody produced against the peptide sequence from one of the expressed genes, which was detected in the crop epithelium, particularly in the apical portions of the cells. Furthermore, we also showed an increase in sugar concentration in a sucrose solution collected from the crop lumen a few minutes after feeding, indicating that water uptake occurs during storage of nectar in the crop, suggesting a previously unidentified function for the honeybee crop.