Investigating the Regulation of Hypopharyngeal Gland Activity in Honeybees (Apis mellifera carnica) Under Overwintering Conditions via Morphologic Analysis Combined With iTRAQ-Based Comparative Proteomics

The management of overwintering honeybee colonies is pivotal for the apiculture industry in China.To investigate the molecular mechanisms involved in the seasonal regulation of the development of Apis mellifera carnicas hypopharyngeal gland (HG), transmission electron microscopy (TEM), and large-scale proteomics (isobaric tag for relative and absolute quantification; iTRAQ) were employed. In total, 3,025 proteins were identified at twotime points: winter (constituting group A) and early spring (constituting group B). Among them, 24 proteins were quantified and compared to identify their differential expression patterns. The TEM profiles and iTRAQ analysis results might aid in understanding the molecular mechanisms associated with the seasonal changes in honeybee HG. For example, the acinar cells of spring worker honeybees had more mature organelles. Furthermore, the ribosomal structures and protein biosynthesis were strengthened. However, the amount of exocrine royal jelly produced could not have satisfied the demand of the feeding larvae and queen. Honeybees might suffer reduced immune function during their feeding stage. The present study elucidates the regulatory mechanisms of HG on overwintering and spring arousal in honeybees. The results might provide a practical and theoretical guideline for the overwintering management program of the apicultural industry.