BACKGROUND: In the honeybee Apis mellifera, female larvae destined to become a queen are fed with royal jelly, a
secretion of the hypopharyngeal glands of young nurse bees that rear the brood. The protein moiety of royal jelly
comprises mostly major royal jelly proteins (MRJPs) of which the coding genes (mrjp1-9) have been identified on
chromosome 11 in the honeybee’s genome.
RESULTS: We determined the expression of mrjp1-9 among the honeybee worker caste (nurses, foragers) and the
sexuals (queens (unmated, mated) and drones) in various body parts (head, thorax, abdomen). Specific mrjp
expression was not only found in brood rearing nurse bees, but also in foragers and the sexuals.
CONCLUSIONS: The expression of mrjp1 to 7 is characteristic for the heads of worker bees, with an elevated
expression of mrjp1-4 and 7 in nurse bees compared to foragers. Mrjp5 and 6 were higher in foragers compared to
nurses suggesting functions in addition to those of brood food proteins. Furthermore, the expression of mrjp9 was
high in the heads, thoraces and abdomen of almost all female bees, suggesting a function irrespective of body
section. This completely different expression profile suggests mrjp9 to code for the most ancestral major royal
jelly protein of the honeybee.