Varroa destructor injects a salivary secretion into honeybees during their feeding process. The salivary secretion plays a vital role in mite–bee interactions and is the main cause of honeybee illness. To determine the biological function of cystatin-L2-like, one of the components of V. destructor salivary secretion, its gene expression in mites during the reproductive phase and dispersal phase was quantified using RT-qPCR, respectively. Moreover, the E. coli-expressed and -purified cystatin was injected into the white-eyed honeybee pupae, and its effects on the survival, the weight of the newly emerged bee, and the transcriptome were determined. The results showed that cystatin was significantly upregulated in mites during the reproductive phase. Cystatin significantly shortened the lifespan of pupae and decreased the weight of the newly emerged bees. Transcriptome sequencing showed that cystatin upregulated 1496 genes and downregulated 1483 genes in pupae. These genes were mainly enriched in ATP synthesis, the mitochondrial respiratory chain, and cuticle structure and function. Cystatin comprehensively downregulated the metabolism of carbohydrates, fatty acids, and amino acids, and energy production in the pupae. The downregulation of metabolic activity could save more nutrients and energy for V. destructor, helping it to maximize its reproduction potential, implying that the mite could manipulate the metabolism of host bees through the injected salivary secretion. The results provide new insights into mite–bee interactions, providing a basis for related studies and applications.

Vespa velutina (V. velutina) is a globally widespread predator of honeybees, posing a serious threat to them. Apis cerana (A. cerana) has acquired the ability to partially thwart the predation of the wasps, but the molecular mechanism by which it responds to V. velutina attacks is unknown. Here, both transcriptomic and metabolomic analyses were integrated to decipher what happened in the brain tissues of A. cerana exposed to V. velutina attacks. Transcriptomic analysis revealed 296 differentially expressed genes (DEGs) that were significantly enriched in neural signaling pathways (particularly serotonin and dopamine transmission), the cAMP signaling pathway, and energy metabolism. Metabolomic results showed that V. velutina attacks affected 38 metabolic pathways involving 86 differentially expressed metabolites (DEMs), primarily including amino acids, nucleotides, and carbohydrates. Several metabolites, such as isocitrate, xanthine, and adenosine, were upregulated in response to the hornet presence. Combined pathway analysis indicated an upregulation of the purine and tyrosine metabolism pathways, highlighting their critical role in A. cerana against invasive hornets. The results of this study will help to understand the molecular mechanisms of A. cerana in response to V. velutina attacks and provide valuable insights for enhancing collective defensive behavior against V. velutina in honeybees.

High temperature is normally harmful to an organism. However, honey bees evolve, maintaining a relatively higher colony temperature of 34.5 °C in the long reproduction period. To determine the effect of such a higher colony temperature on adult bees and its biological significance, newly emerged bees were reared in cages at 34.5 °C and room temperature of 25.0 °C, respectively. Their survival rate, head weight, royal jelly-secreting gene expression, and morphology of the hypopharyngeal gland were investigated. Moreover, 40-day-old bees with significant differences in survival rate between the two temperature groups were subject to transcriptome and lipidome analysis. The result showed that the higher colony temperature was overall negative for the bees’ longevity. Transcriptome analysis showed that fatty acid metabolism-related items were enriched and the involved genes were upregulated in honey bees reared at 34.5 °C compared with the honey bees reared at 25.0 °C. Lipidomic analysis further validated that fatty acid metabolism, especially sphingolipid metabolism, was significantly altered. Such upregulation of fatty acid metabolism-related genes was also detected in young adult bees of 5 days old reared at 34.5 °C. These bees had heavier head weights, higher expression of royal jelly-secreting-related genes, and more developed hypopharyngeal glands. Such results showed that the colony temperature of 34.5 °C could accelerate the development process of newly emerged bees to be nurse bees, significantly increasing the colony nurturing capability, which in turn increased the development speed, size, and survivability of the colony. Thereby, the colony temperature of 34.5 °C shortened the lifespan of individual bees, but obtained huge returns at the colony level, with remarkable biological significance.