The ambient temperature and relative humidity affect the metabolic and physiological responses of bees, thus affecting their life activities. However, the physiological changes in bee due to high temperature and high humidity remain poorly understood. In this study, we explored the effects of higher temperature and humidity on the epiphysiology of bees by evaluating the survival, tolerance and body water loss in two bee species ( Apis cerana and Apis mellifera ). We also evaluated the changes in the activity of antioxidant and detoxification enzymes in their body. We observed that under higher temperature and humidity conditions, the survival rate of A . mellifera was higher than that of A . cerana . On the other hand, a comparison of water loss between the two species revealed that A . mellifera lost more water. However, under extremely high temperature conditions, A . cerana was more tolerant than A . mellifera . Moreover, under higher temperature and humidity conditions, the activity of antioxidant and detoxification enzymes in bees was significantly increased. Overall, these results suggest that high temperatures can adversely affect bees. They not only affect the survival and water loss, but also stimulate oxidative stress in bees. However, unlike our previous understanding, high humidity can also adversely affect bees, although its effects are lower than that of temperature.

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The biological activity and geographical distribution of honey bees is strongly temperature-dependent, due to their ectothermic physiology. In China, the endemic Apis cerana cerana exhibits stronger cold hardiness than Western honey bees, making the former species important pollinators of winter-flowering plants. Although studies have examined behavioral and physiological mechanisms underlying cold resistance in bees, data are scarce regarding the exact molecular mechanisms. Here, we investigated gene expression in A. c. cerana under two temperature treatments, using transcriptomic analysis to identify differentially expressed genes (DEGs) and relevant biological processes, respectively. Across the temperature treatments, 501 DEGs were identified. A gene ontology analysis showed that DEGs were enriched in pathways related to sugar and amino acid biosynthesis and metabolism, as well as calcium ion channel activity. Additionally, heat shock proteins, zinc finger proteins, and serine/threonine-protein kinases were differentially expressed between the two treatments. The results of this study provide a general digital expression profile of thermoregulation genes responding to cold hardiness in A. c. cerana. Our data should prove valuable for future research on cold tolerance mechanisms in insects, and may be beneficial in breeding efforts to improve bee hardiness.

Chemosensory genes play a central role in sensing chemical signals and guiding insect behavior. The Chinese honeybee, Apis cerana cerana, is one of the most important insect species in China in terms of resource production, and providing high-quality products for human consumption, and also serves as an important pollinator. Communication and foraging behavior of worker bees is likely linked to a complex chemosensory system. Here, we used transcriptome sequencing on adult A. c. cerana workers of different ages to identify the major chemosensory gene families and the differentially expressed genes(DEGs), and to investigate their expression profiles. A total of 109 candidate chemosensory genes in five gene families were identified from the antennal transcriptome assemblies, including 17 OBPs, 6 CSPs, 74 ORs, 10 IRs, and 2SNMPs, in which nineteen DEGs were screened and their expression values at different developmental stages were determined in silico. No chemosensory transcript was specific to a certain developmental period. Thirteen DEGs were upregulated and 6were downregulated. We created extensive expression profiles in six major body tissues using qRT-PCR and found that most DEGs were exclusively or primarily expressed in antennae. Others were abundantly expressed in the other tissues, such as head, thorax, abdomen, legs, and wings. Interestingly, when a DEG was highly expressed in the thorax, it also had a high level of expression in legs, but showed a lowlevel in antennae. This study explored five chemoreceptor superfamily genes using RNA-Seq coupled with extensive expression profiling of DEGs. Our results provide new insights into the molecular mechanism of odorant detection in the Asian honeybee and also serve as an extensive novel resource for comparing and investigating olfactory functionality in hymenopterans.

Coordination in honeybees is heavily dependent on their chemoreception system, in which odorantbinding proteins are very important. A previous study based on the antennal transcriptome of Apis cerana cerana revealed that OBP15 was significantly up-regulated at 25-day-old. To further unravel and clarify its functional role, we first cloned and characterized AcerOBP15 from the antennae of worker bees. Sequence and phylogenetic analysis showed that AcerOBP15 belongs to the Minus-C OBPs family. AcerOBP15 was primarily expressed in forager antennae and legs. A fluorescent binding assay showed that AcerOBP15 had strong binding affinity to most floral volatiles, a restricted number of bee pheromone components and non-volatile compounds, among which the highest is myrcene. Based on RNAi and EAG assays, AcerOBP15 may be required for myrcene recognition. Taken together, we suggest that AcerOBP15 plays a dual role in olfactory and gustatory reception when foraging. Our study lays a theoretical foundation for further studies regarding the mechanism of chemoreception in A. cerana cerana .