The genome of the western honeybee (Apis mellifera) harbors nine transcribed 
major royal jelly protein genes (mrjp1-9) which originate from a single-copy 
precursor via gene duplication. The first MRJP was identified in royal jelly, a 
secretion of the bees' hypopharyngeal glands that is used by young worker bees, 
called nurses, to feed developing larvae. Thus, MRJPs are frequently assumed to 
mainly have functions for developing bee larvae and to be expressed in the food 
glands of nurse bees. In-depth knowledge on caste- and age-specific role and 
abundance of MRJPs is missing. We here show, using combined quantitative 
real-time PCR with quantitative mass spectrometry, that expression and protein 
amount of mrjp1-5 and mrjp7 show an age-dependent pattern in worker's 
hypopharyngeal glands as well as in brains, albeit lower relative abundance in 
brains than in glands. Expression increases after hatching until the nurse bee 
period and is followed by a decrease in older workers that forage for plant 
products. Mrjp6 expression deviates considerably from the expression profiles of 
the other mrjps, does not significantly vary in the brain, and shows its highest 
expression in the hypopharyngeal glands during the forager period. Furthermore, 
it is the only mrjp of which transcript abundance does not correlate with 
protein amount. Mrjp8 and mrjp9 show, compared to the other mrjps, a very low 
expression in both tissues. Albeit mrjp8 mRNA was detected via qPCR, the protein 
was not quantified in any of the tissues. Due to the occurrence of MRJP8 and 
MRJP9 in other body parts of the bees, for example, the venom gland, they might 
not have a hypopharyngeal gland- or brain-specific function but rather functions 
in other tissues. Thus, mrjp1-7 but not mrjp8 and mrjp9 might be involved in the 
regulation of phenotypic plasticity and age polyethism in worker honeybees.