Transcriptomic Analysis of Hemolymph in Pollen-Foraging and Non-Pollen-Foraging Apis mellifera ligustica and Identification of Candidate Genes

Foraging is a physiologically demanding behavior in honey bees, requiring substantial energy expenditure and continuous physiological adaptation. To investigate the molecular responses of hemolymph during foraging, pollen-foraging workers returning from pear flowers and non-foraging workers of Apis mellifera ligustica were subjected to hemolymph transcriptome sequencing using the Illumina platform. Differentially expressed genes (DEGs) were identified, followed by Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses, and quantitative real-time PCR (qRT-PCR) validation. A total of 563 DEGs were identified between the two groups, including 323 upregulated and 240 downregulated genes. GO analysis indicated that these genes were mainly associated with proteolysis, peptidase activity, serine hydrolase activity, and cell–cell adhesion. KEGG enrichment analysis showed significant enrichment in lysosome, efferocytosis, protein processing in the endoplasmic reticulum, and metabolic pathways. Unlike classical immune pathways, Toll and Imd signaling showed no significant enrichment. Integrating transcriptomic analysis and qRT-PCR validation identified four candidate genes, ADAM10-X1, Drpr-X2, CPT1A, and Lipase3, which are associated with cellular homeostasis, lipid metabolism, and nutrient utilization. These findings demonstrate that foraging primarily induces metabolic and homeostatic remodeling of the hemolymph rather than broad activation of canonical immune pathways. This study provides new insights into the molecular mechanisms underlying physiological adaptation to foraging in Apis mellifera ligustica and identifies candidate genes for future studies of honey bee nutritional physiology and behavioral regulation.