Phosphoproteomic Analysis of Protein Phosphorylation Networks in the Hypopharyngeal Gland of Honeybee Workers (Apis mellifera ligustica).

The hypopharyngeal gland (HG) in honeybee workers changes functions according to physiological age in the bee colony from producing royal jelly (RJ) in nurse bees to digestive enzymes in foragers. The same set of secretory cells expresses different genes or proteins to create these age-dependent changes; however, it is unknown precisely how the phosphorylation network regulates physiological differences across the development of the adult worker HG. We employed high-accuracy mass-spectrometry-based proteomics to survey phosphoproteome changes in the newly emerged, nurse, and forager bees. Overall, 941, 1322, and 1196 phosphorylation sites matching 1007, 1353, and 1199 phosphopeptides from 549, 720, and 698 phosphoproteins were identified in the three ages of the HG, respectively. Specialized, interconnected phosphorylation networks within each age were found by comparing protein abundance and phosphorylation levels. This illustrates that many proteins are regulated by phosphorylation independent of their expression levels. Furthermore, proteins in key biological processes and pathways were dynamically phosphorylated with age development, including the centrosome cycle, mitotic spindle elongation, macromolecular complex disassembly, and ribosome, indicating that phosphorylation tunes protein activity to optimize cellular behavior of the HG over time. Moreover, complementary protein and phosphoprotein expression is required to support the unique physiology of secretory activity in the HG. This reported data set of the honeybee phosphoproteome significantly improves our understanding of a range of regulatory mechanisms controlling a variety of cellular processes and will serve as a valuable resource for those studying the honeybee and other insects.