Honeybee (Apis mellifera) exhibits divisions in both morphology and reproduction. The queen is larger in size and fully developed sexually, while the worker bees are smaller in size and nearly infertile. To better understand the specific time and underlying molecular mechanisms of caste differentiation, the proteomic profiles of larvae intended to grow into queen and worker castes were compared at 72 and 120 hours using two dimensional electrophoresis (2-DE), network, enrichment and quantitative PCR analysis. There were significant differences in
protein expression between the two larvae castes at 72 and 120 hours, suggesting the queen and the worker larvae have already decided their fate before 72 hours. Specifically, at 72 hours, queen intended larvae over-expressed
transketolase,
aldehyde reductase, and
enolase proteins which are involved in carbohydrate metabolism and energy production, imaginal disc
growth factor 4 which is a developmental related
protein,
long-chain-fatty-acid CoA ligase and
proteasome subunit alpha type 5 which metabolize fatty and
amino acids, while worker intended larvae over-expressed
ATP synthase beta subunit,
aldehyde dehydrogenase,
thioredoxin peroxidase 1 and
peroxiredoxin 2540, lethal (2) 37 and
14-3-3 protein epsilon,
fatty acid binding protein, and translational controlled
tumor protein. This differential
protein expression between the two caste intended larvae was more pronounced at 120 hours, with particular significant differences in
proteins associated with carbohydrate metabolism and energy production. Functional enrichment analysis suggests that carbohydrate metabolism and energy production and anti-oxidation
proteins play major roles in the formation of caste divergence. The constructed network and validated gene expression identified target
proteins for further functional study. This new finding is in contrast to the existing notion that 72 hour old larvae has bipotential and can develop into either queen or worker based on epigenetics and can help us to gain new insight into the time of departure as well as caste trajectory influencing elements at the molecular level.