How Honeybees Defy Gravity with Royal Jelly to Raise Queens

Reminiscences on the honeybee genome project and the rise of epigenetic concepts in insect science

The sequencing of the honeybee genome in 2006 was an important technological and logistic achievement experience. But what benefits have flown from the honeybee genome project? What does the annotated genomic assembly mean for the study of behavioural complexity and organismal function in honeybees? Here, I discuss several lines of research that have arisen from this project and highlight the rapidly expanding studies on insect epigenomics, emergent properties of royal jelly, the mechanism of nutritional control of development and the contribution of epigenomic regulation to the evolution of sociality. I also argue that the term 'insect epigenetics' needs to be carefully redefined to reflect the diversity of epigenomic toolkits in insects and the impact of lineage-specific innovations on organismal outcomes. The honeybee genome project helped pioneer advances in social insect molecular biology, and fuelled breakthrough research into the role of flexible epigenomic control systems in linking genotype to phenotype.

Expression of honey bee (Apis mellifera) sterol homeostasis genes in food jelly producing glands of workers

Adult workers of Western honey bees (Apis mellifera L.) acquire sterols from their pollen diet. These food sterols are transported by the hemolymph to peripheral tissues such as the mandibular and the hypopharyngeal glands in the worker bees' heads that secrete food jelly which is fed to developing larvae. As sterols are obligatory components of biological membranes and essential precursors for molting hormone synthesis in insects, they are indispensable to normal larval development. Thus, the study of sterol delivery to larvae is important for a full understanding of honey bee larval nutrition and development. Whereas hypopharyngeal glands only require sterols for their membrane integrity, mandibular glands add sterols, primarily 24-methylenecholesterol, to its secretion. For this, sterols must be transported through the glandular epithelial cells. We have analyzed for the first time in A. mellifera the expression of genes which are involved in intracellular movement of sterols. Mandibular and hypopharyngeal glands were dissected from newly emerged bees, 6-day-old nurse bees that feed larvae and 26-day-old forager bees. The expression of seven genes involved in intracellular sterol metabolism was measured with quantitative real-time PCR. Relative transcript abundance of sterol metabolism genes was significantly influenced by the age of workers and specific genes but not by gland type. Newly emerged bees had significantly more transcripts for six out of seven genes than older bees indicating that the bulk of the proteins needed for sterol metabolism are produced directly after emergence.

Royal Jelly: Biological Action and Health Benefits

Royal jelly (RJ) is a highly nutritious natural product with great potential for use in medicine, cosmetics, and as a health-promoting food. This bee product is a mixture of important compounds, such as proteins, vitamins, lipids, minerals, hormones, neurotransmitters, flavonoids, and polyphenols, that underlie the remarkable biological and therapeutic activities of RJ. Various bioactive molecules like 10-hydroxy-2-decenoic acid (10-HDA), antibacterial protein, apisin, the major royal jelly proteins, and specific peptides such as apisimin, royalisin, royalactin, apidaecin, defensin-1, and jelleins are characteristic ingredients of RJ. RJ shows numerous physiological and pharmacological properties, including vasodilatory, hypotensive, antihypercholesterolaemic, antidiabetic, immunomodulatory, anti-inflammatory, antioxidant, anti-aging, neuroprotective, antimicrobial, estrogenic, anti-allergic, anti-osteoporotic, and anti-tumor effects. Moreover, RJ may reduce menopause symptoms and improve the health of the reproductive system, liver, and kidneys, and promote wound healing. This article provides an overview of the molecular mechanisms underlying the beneficial effects of RJ in various diseases, aging, and aging-related complications, with special emphasis on the bioactive components of RJ and their health-promoting properties. The data presented should be an incentive for future clinical studies that hopefully will advance our knowledge about the therapeutic potential of RJ and facilitate the development of novel RJ-based therapeutic opportunities for improving human health and well-being.

Transcriptome analysis of Apis mellifera antennae reveals molecular divergence underlying the division of labour in worker bees

The olfactory system plays a fundamental role in mediating insect behaviour. Worker bees exhibit an age-dependent division of labour, performing discrete sets of behaviours throughout their lifespan. The behavioural states of bees rely on their sense of the environment and chemical communication via their olfactory system, the antennae. However, the olfactory adaptation mechanism of worker bees during their behavioural development remains unclear. In this study, we conducted a comprehensive and quantitative analysis of antennal gene expression in the Apis mellifera of newly emerged workers, nurses, foragers and defenders using RNA-seq. We found that the antenna tissues of honey bees continued developing after transformation from newly emerged workers to adults. Additionally, we identified differentially expressed genes associated with bee development and division of labour. We validated that major royal jelly protein genes are highly and specifically expressed in nurse honey bee workers. Furthermore, we identified and validated significant alternative splicing events correlated with the development and division of labour. These findings provide a comprehensive transcriptome profile and a new perspective on the molecular mechanisms that may underlie the worker honey bee division of labour.

Mandibular glands secrete 24-methylenecholesterol into honey bee (Apis mellifera) food jelly

Honey bee (Apis mellifera) workers feed their larvae with food jelly that is secreted by specialized glands in their heads - the hypopharyngeal and the mandibular glands. Food jelly contains all the nutrients the larvae need to develop into adult honey bees, including essential dietary sterols. The main sterol in food jelly, 24-methylenecholesterol (24MC), is pollen-derived and delivered in food jelly to the larvae in a complex with two proteins, major royal jelly protein 1 (MRJP1) and apisim. Whereas the proteins are synthesized in the hypopharyngeal glands, the sterol-secreting gland has not been identified. We here identified the mandibular glands as sterol-secreting gland for food jelly production by direct detection of the four main honey bee sterols (24MC, campesterol, β-sitosterol and isofucosterol). Furthermore, 24MC seems to be specifically enriched in the mandibular glands, thereby ensuring that food jelly contains the amounts of 24MC necessary for complex formation with MRJP1 and apisimin.

Exploring the Potential of Bee-Derived Antioxidants for Maintaining Oral Hygiene and Dental Health: A Comprehensive Review

Honey bee products comprise various compounds, including honey, propolis, royal jelly, bee pollen, bee wax and bee venom, which have long been recognized for their pharmacological and health-promoting benefits. Scientists have discovered that periodontal disorders stem from dental biofilm, an inflammatory response to bacterial overgrowth produced by dysbiosis in the oral microbiome. The bee products have been investigated for their role in prevention of oral diseases, which are attributed to a myriad of biologically active compounds including flavonoids (pinocembrin, catechin, caffeic acid phenethyl ester (CAPE) and galangin), phenolic acids (hydroxybenzoic acid, hydroxycinnamic acid, p-coumaric, ellagic, caffeic and ferulic acids) and terpenoids. This review aims to update the current understanding of role of selected bee products, namely, honey, propolis and royal jelly, in preventing oral diseases as well as their potential biological activities and mechanism of action in relation to oral health have been discussed. Furthermore, the safety of incorporation of bee products is also critically discussed. To summarize, bee products could potentially serve as a therapy option for people suffering from a variety of oral disorders.

Quantitative comparison of manuka and clover honey proteomes with royal jelly

Royal jelly and honey are two substances produced successively by the worker bee caste. Modern proteomics approaches have been used to explore the protein component of each substance independently, but to date none have quantitatively compared the protein profile of honey and royal jelly directly. Sequential window acquisition of all theoretical fragment-ion spectra mass spectrometry (SWATH-MS) was used to compare protein quantities of bee origin in mānuka and clover honey to royal jelly. Two analysis techniques identified 76 proteins in total. Peptide intensity was directly compared for a subset of 31 proteins that were identified with high confidence, and the relative changes in protein abundance were compared between each honey type and royal jelly. Major Royal Jelly Proteins (MRJPs) had similar profiles in both honeys, except MRJP6, which was significantly more abundant in clover honey. Proteins involved in nectar metabolism were more abundant in honey than in royal jelly as expected. However, the trend revealed a potential catalytic role for MRJP6 in clover honey and a nectar- or honey-specific role for uncharacterised protein LOC408608. The abundance of MRJP6 in mānuka honey was equivalent to royal jelly suggesting a potential effect of nectar type on expression of this protein. Data are available via ProteomeXchange with identifier PXD038889.

Current Status of the Bioactive Properties of Royal Jelly: A Comprehensive Review with a Focus on Its Anticancer, Anti-Inflammatory, and Antioxidant Effects

Royal jelly (RJ) has been one of the most widely used natural products in alternative medicine for centuries. Being produced by both hypopharyngeal and mandibular glands, RJ exhibits an extraordinary complexity in terms of its composition, including proteins, lipids, carbohydrates, polyphenols, vitamins, and hormones. Due to its heterogeneous structure, RJ displays various functional roles for honeybees, including being involved in nutrition, learning, memory, and social behavior. Furthermore, a wide range of studies reported its therapeutic properties, including anticancer, anti-inflammatory, and antioxidant activities, to name a few. In this direction, there is a wide range of health-related problems for which the medical area specialists and researchers are continuously trying to find a cure, such as cancer, atherosclerosis, or infertility. For the mentioned diseases and more, it has been proven that RJ is a key player in finding a valuable treatment. In this review, the great impact of RJ as an alternative medicine agent is highlighted, with a focus on its anticancer, anti-inflammatory, and antioxidant activities. Moreover, we link it to its apitherapeutic potential by discussing its composition. Herein, we discuss a wide range of novel studies and present the latest research work.

The Potential Effect of Royal Jelly on Biomarkers Related to COVID-19 Infection and Severe Progression

Royal jelly is a yellowish to white gel-like substance that is known as a "superfood" and consumed by queen bees. There are certain compounds in royal jelly considered to have health-promoting properties, including 10-hydroxy-2-decenoic acid and major royal jelly proteins. Royal jelly has beneficial effects on some disorders such as cardiovascular disease, dyslipidemia, multiple sclerosis, and diabetes. Antiviral, anti-inflammatory, antibacterial, antitumor, and immunomodulatory properties have been ascribed to this substance. This chapter describes the effects of royal jelly on COVID-19 disease.

Honey bee symbiont buffers larvae against nutritional stress and supplements lysine

Honey bees have suffered dramatic losses in recent years, largely due to multiple stressors underpinned by poor nutrition [1]. Nutritional stress especially harms larvae, who mature into workers unable to meet the needs of their colony [2]. In this study, we characterize the metabolic capabilities of a honey bee larvae-associated bacterium, Bombella apis (formerly Parasaccharibacter apium), and its effects on the nutritional resilience of larvae. We found that B. apis is the only bacterium associated with larvae that can withstand the antimicrobial larval diet. Further, we found that B. apis can synthesize all essential amino acids and significantly alters the amino acid content of synthetic larval diet, largely by supplying the essential amino acid lysine. Analyses of gene gain/loss across the phylogeny suggest that four amino acid transporters were gained in recent B. apis ancestors. In addition, the transporter LysE is conserved across all sequenced strains of B. apis. Finally, we tested the impact of B. apis on developing honey bee larvae subjected to nutritional stress and found that larvae supplemented with B. apis are bolstered against mass reduction despite limited nutrition. Together, these data suggest a novel role of B. apis as a nutritional mutualist of honey bee larvae.

Royal Jelly Proteins and Their Derived Peptides: Preparation, Properties, and Biological Activities

Royal jelly, also called bee milk, is a source of high-quality proteins. Royal jelly proteins serve as not only a rich source of essential amino acids and functional donors but also an excellent substrate for preparing bioactive peptides. Most naturally occurring bioactive peptides in royal jelly are antibacterial, while peptides derived from proteolytic reactions are shown to exert antihypertensive, antioxidative, and anti-aging activities. Further studies are warranted to characterize the functional properties of major royal jelly proteins and peptides, to explore the preparation of bioactive peptides and the potential novel activities, to improve their bioavailability, to enhance the production efficiency for commercial availability, and finally to open up new applications for royal jelly as a functional food and potential therapeutic agent.

Reproductive Potential Accelerates Preimaginal Development of Rebel Workers in Apis mellifera

Simple Summary

All female honeybee larvae may develop into workers or queens, depending on the food they receive. During this period, queen mandibular pheromones (QMP) perform a regulatory function in inhibiting ovarian development in adult workers. These pheromones are transmitted (via trophallaxis) by workers to pass information to larvae on the presence or absence of the queen. Queen-less conditions are conducive to the emergence of rebel workers that are set to reproduce, and do not participate in the rearing of successive bee generations in contrast to the sterile, normal workers. We posited that rebels are not only similar to queens in some anatomical features, but also develop in a shorter time in comparison to normal workers. Therefore, the aim of this study was to compare the duration of preimaginal development in rebel and normal workers. Our results confirmed that the workers who develop in a queen-less colony undergo a shorter preimaginal development than those in a queen-right colony.

Abstract

Rebel workers develop from eggs laid by the previous queen, before it went swarming and left the colony orphaned, until the emergence of a new queen. In contrast to normal workers developing in the queen’s presence, rebels are set to reproduce and avoid rearing of successive bee generations. They have more ovarioles in their ovaries, as well as more developed mandibular glands and underdeveloped hypopharyngeal glands, just like the queen. We posited that rebels are not only similar to queens in some anatomical features, but also develop in a shorter time in comparison to normal workers. Therefore, the aim of this study was to compare preimaginal development duration in rebel and normal workers. The results show that rebels, i.e., workers with a higher reproductive potential, had a significantly shorter preimaginal development period (mean ± SD, 19.24 ± 0.07 days) than normal workers (22.29 ± 0.32 days). Our result confirmed that workers who develop in a queen-less colony undergo a shorter preimaginal development than those in a queen-right colony.

Evaluating and Comparing the Natural Cell Structure and Dimensions of Honey Bee Comb Cells of Chinese Bee, Apis cerana cerana (Hymenoptera: Apidae) and Italian Bee, Apis mellifera ligustica (Hymenoptera: Apidae)

The hexagonal structure of the honey bee comb cell has been the source of many studies attempting to understand its structure and function. In the storage area of the comb, only honey is stored and no brood is reared. We predicted that honey bees may construct different hexagonal cells for brood rearing and honey storage. We used quantitative analyses to evaluate the structure and function of the natural comb cell in the Chinese bee, Apis cerana cerana and the Italian bee, A. mellifera ligustica. We made cell molds using a crystal glue solution and measured the structure and inclination of cells. We found that the comb cells of A. c. cerana had both upward-sloping and downward-sloping cells; while the A. m. ligustica cells all tilted upwards. Interestingly, the cells did not conform to the regular hexagonal prism structure and showed irregular diameter sizes. In both species, comb cells also were differentiated into worker, drone and honey cells, differing in their diameter and depth. This study revealed unique differences in the structure and function of comb cells and showed that honey bees design their cells with precise engineering to increase storage capacity, and to create adequate growing room for their brood.

Formulation of Ocular In Situ Gels with Lithuanian Royal Jelly and Their Biopharmaceutical Evaluation In Vitro

Royal jelly is a natural substance produced by worker bees that possesses a variety of biological activities, including antioxidant, anti-inflammatory, antibacterial, and protective. Although fresh royal jelly is kept at low temperatures, to increase its stability, it needs to be incorporated into pharmaceutical formulations, such as in situ gels. The aim of this study was to formulate in situ ocular gels containing Lithuanian royal jelly for topical corneal use in order to increase the retention time of the formulation on the ocular surface and bioavailability. Gels were evaluated for physicochemical characteristics (pH, rheological properties, refractive index) and in vitro drug release measuring the amount of 10-hydroxy-2-decenoic acid (10-HDA). An ocular irritation test and cell viability tests were performed using the SIRC (Statens Seruminstitut Rabbit Cornea) cell culture line. Results indicated that all the in situ gels were within an acceptable pH and refractive index range close to corneal properties. Rheology studies have shown that the gelation temperature varies between 25 and 32 °C, depending on the amount of poloxamers. The release studies have shown that the release of 10-HDA from in situ gels is more sustained than royal jelly suspension. All gel formulations were non-irritant according to the short-time exposure test (STE) using the SIRC cell culture line, and long-term cell viability studies indicated that the formulations used in small concentrations did not induce cell death. Prepared in situ gels containing royal jelly have potential for ocular drug delivery, and they may improve the bioavailability, stability of royal jelly, and formation of non-irritant ocular formulations.

Methionine as a methyl donor regulates caste differentiation in the European honey bee (Apis mellifera)

Nutrition contributes to honey bee caste differentiation, but the role of individual nutrients is still unclear. Most essential amino acid contents, except that of methionine (Met), are greater in royal jelly than worker jelly. After ∼3.5 d, the Met content in the latter was slightly greater than in the former. Met is the major raw material used in the synthesis of S-adenosyl-L-methionine, an active methyl donor for DNA methylation, which is an epigenetic driver of caste differentiation. Here, we tested whether Met regulates caste differentiation in honey bees by determining its effects on the caste development of bees receiving four diets: the basic, basic + 0.2% Met, basic + 0.2% Met + 20 mg/kg 5-azacytidine, and basic + 20 mg/kg 5-azacytidine. The presence of Met decreased the adult bee body length and the numbers of ovarioles, indicating that Met may direct the development of female larvae toward worker bees. The upregulated expression of SAMS, Dnmt1, and Dnmt3 caused by Met exposure in 4-d-old larvae indicated that the worker-inductive effects of Met may occur through the promotion of DNA methylation. We investigated the co-effects of Met and glucose on bee development, and found that the effects of an increased glucose level on the number of ovarioles and body length did not strengthen the worker-inductive effects caused by Met. Our results contribute to caste development theory and suggest that Met-as a methyl donor-plays a regulatory, but not decisive, role in caste differentiation.

Mining the Royal Jelly Proteins: Combinatorial Hexapeptide Ligand Library Significantly Improves the MS-Based Proteomic Identification in Complex Biological Samples

Royal jelly (RJ) is a complex, creamy secretion produced by the glands of worker bees. Due to its health-promoting properties, it is used by humans as a dietary supplement. However, RJ compounds are not fully characterized yet. Hence, in this research, we aimed to broaden the knowledge of the proteomic composition of fresh RJ. Water extracts of the samples were pre-treated using combinatorial hexapeptide ligand libraries (ProteoMiner^TM kit), trypsin-digested, and analyzed by a nanoLC-MALDI-TOF/TOF MS system. To check the ProteoMiner^TM performance in the MS-based protein identification, we also examined RJ extracts that were not prepared with the ProteoMiner^TM kit. We identified a total of 86 proteins taxonomically classified to Apis spp. (bees). Among them, 74 proteins were detected in RJ extracts pre-treated with ProteoMiner^TM kit, and only 50 proteins were found in extracts non-enriched with this technique. Ten of the identified features were hypothetical proteins whose existence has been predicted, but any experimental evidence proves their in vivo expression. Additionally, we detected four uncharacterized proteins of unknown functions. The results of this research indicate that the ProteoMiner^TM strategy improves proteomic identification in complex biological samples. Broadening the knowledge of RJ composition may contribute to the development of standards and regulations, enhancing the quality of RJ, and consequently, the safety of its supplementation.

Colloidal structure of honey and its influence on antibacterial activity

Honey colloidal structure emerges as a new trend in research on honey functions since it became recognized as a major factor altering bioactivity of honey compounds. In honey complex matrix, macromolecules self-associate to colloidal particles at the critical concentration, driven by honey viscosity. Sequestration of macromolecules into colloids changes their activities and affects honey antibacterial function. This review fills the 80-year-old gap in research on honey colloidal structure. It summarizes past and current status of the research on honey colloids and describes physicochemical properties and the mechanisms of colloid formation and their dissociation upon honey dilution. The experimental observations are explained in the context of theoretical background of colloidal science. The functional changes and bioactivity of honey macromolecules bound to colloidal particles are illustrated here by the production of H₂ O₂ by glucose oxidase and the effect they have on antibacterial activity of honey. The changes in the production of H₂ O₂ and antibacterial activity of honey were coordinated with the changes in the aggregation-dissociation states of honey colloidal particles upon dilution. In all cases, these changes were nonlinear, assuming an inverted U-shaped dose-response curve. At the curve maximum, the production of H₂ O₂ and antibacterial activity reached the peak. The curve maximum signaled the minimum honey concentration required for the phase separation. With phase transition from two-phase colloidal condense state to dilute state dispersion, the change to opposite effects of dilution on these honey's activities occurred. Thus, the colloidal structure strongly influences bioactivity of honey compounds and affects its antibacterial activity.

Health Promoting Properties of Bee Royal Jelly: Food of the Queens

Royal jelly (RJ) demand is growing every year and so is the market for functional foods in general. RJ is formed by different substances, mainly carbohydrates, proteins, and lipids, but also vitamins, minerals, and phenolic or volatile compounds in lower proportion. Major royal jelly proteins (MRJP) are, together with 10-hydroxy-2-decenoic acid (10-HDA), key substances of RJ due to their different biological properties. In particular, 10-HDA is a unique substance in this product. RJ has been historically employed as health enhancer and is still very relevant in China due to the traditional medicine and the apitherapy. Nowadays, it is mainly consumed as a functional food or is found in supplements and other formulations for its health-beneficial properties. Within these properites, anti-lipidemic, antioxidant, antiproliferative, antimicrobial, neuroprotective, anti-inflammatory, immunomodulatory, antiaging, and estrogenic activities have been reported for RJ or its specific components. This manuscript is aimed at reviewing the current knowledge on RJ components, their assessment in terms of authenticity, their biological activities, and related health applications.

Structure of native glycolipoprotein filaments in honeybee royal jelly

Royal jelly (RJ) is produced by honeybees (Apis mellifera) as nutrition during larval development. The high viscosity of RJ originates from high concentrations of long lipoprotein filaments that include the glycosylated major royal jelly protein 1 (MRJP1), the small protein apisimin and insect lipids. Using cryo-electron microscopy we reveal the architecture and the composition of RJ filaments, in which the MRJP1 forms the outer shell of the assembly, surrounding stacked apisimin tetramers harbouring tightly packed lipids in the centre. The structural data rationalize the pH-dependent disassembly of RJ filaments in the gut of the larvae.

The nuclear and mitochondrial genomes of Frieseomelitta varia - a highly eusocial stingless bee (Meliponini) with a permanently sterile worker caste

BACKGROUND

Most of our understanding on the social behavior and genomics of bees and other social insects is centered on the Western honey bee, Apis mellifera. The genus Apis, however, is a highly derived branch comprising less than a dozen species, four of which genomically characterized. In contrast, for the equally highly eusocial, yet taxonomically and biologically more diverse Meliponini, a full genome sequence was so far available for a single Melipona species only. We present here the genome sequence of Frieseomelitta varia, a stingless bee that has, as a peculiarity, a completely sterile worker caste.

RESULTS

The assembly of 243,974,526 high quality Illumina reads resulted in a predicted assembled genome size of 275 Mb composed of 2173 scaffolds. A BUSCO analysis for the 10,526 predicted genes showed that these represent 96.6% of the expected hymenopteran orthologs. We also predicted 169,371 repetitive genomic components, 2083 putative transposable elements, and 1946 genes for non-coding RNAs, largely long non-coding RNAs. The mitochondrial genome comprises 15,144 bp, encoding 13 proteins, 22 tRNAs and 2 rRNAs. We observed considerable rearrangement in the mitochondrial gene order compared to other bees. For an in-depth analysis of genes related to social biology, we manually checked the annotations for 533 automatically predicted gene models, including 127 genes related to reproductive processes, 104 to development, and 174 immunity-related genes. We also performed specific searches for genes containing transcription factor domains and genes related to neurogenesis and chemosensory communication.

CONCLUSIONS

The total genome size for F. varia is similar to the sequenced genomes of other bees. Using specific prediction methods, we identified a large number of repetitive genome components and long non-coding RNAs, which could provide the molecular basis for gene regulatory plasticity, including worker reproduction. The remarkable reshuffling in gene order in the mitochondrial genome suggests that stingless bees may be a hotspot for mtDNA evolution. Hence, while being just the second stingless bee genome sequenced, we expect that subsequent targeting of a selected set of species from this diverse clade of highly eusocial bees will reveal relevant evolutionary signals and trends related to eusociality in these important pollinators.

Diet quantity influences caste determination in honeybees (Apis mellifera)

In species that care for their young, provisioning has profound effects on offspring fitness. Provisioning is important in honeybees because nutritional cues determine whether a female becomes a reproductive queen or sterile worker. A qualitative difference between the larval diets of queens and workers is thought to drive this divergence; however, no single compound seems to be responsible. Diet quantity may have a role during honeybee caste determination yet has never been formally studied. Our goal was to determine the relative contributions of diet quantity and quality to queen development. Larvae were reared in vitro on nine diets varying in the amount of royal jelly and sugars, which were fed to larvae in eight different quantities. For the middle diet, an ad libitum quantity treatment was included. Once adults eclosed, the queenliness was determined using principal component analysis on seven morphological measurements. We found that larvae fed an ad libitum quantity of diet were indistinguishable from commercially reared queens, and that queenliness was independent of the proportion of protein and carbohydrate in the diet. Neither protein nor carbohydrate content had a significant influence on the first principle component 1 (PC1), which explained 64.4% of the difference between queens and workers. Instead, the total quantity of diet explained a significant amount of the variation in PC1. Large amounts of diet in the final instar were capable of inducing queen traits, contrary to the received wisdom that queen determination can only occur in the third instar. These results indicate that total diet quantity fed to larvae may regulate the difference between queen and worker castes in honeybees.

Towards Precision Nutrition: A Novel Concept Linking Phytochemicals, Immune Response and Honey Bee Health

The high annual losses of managed honey bees (Apis mellifera) has attracted intensive attention, and scientists have dedicated much effort trying to identify the stresses affecting bees. There are, however, no simple answers; rather, research suggests multifactorial effects. Several works have been reported highlighting the relationship between bees' immunosuppression and the effects of malnutrition, parasites, pathogens, agrochemical and beekeeping pesticides exposure, forage dearth and cold stress. Here we analyze a possible connection between immunity-related signaling pathways that could be involved in the response to the stress resulted from Varroa-virus association and cold stress during winter. The analysis was made understanding the honey bee as a superorganism, where individuals are integrated and interacting within the colony, going from social to individual immune responses. We propose the term "Precision Nutrition" as a way to think and study bees' nutrition in the search for key molecules which would be able to strengthen colonies' responses to any or all of those stresses combined.

Hydroxylation patterns associated with pheromone synthesis and composition in two honey bee subspecies Apis mellifera scutellata and A. m. capensis laying workers

Colony losses due to social parasitism in the form of reproductive workers of the Apis mellifera capensis clones results from the production of queen-like pheromonal signals coupled with ovarian activation in these socially parasitic honey bees. While the behavioral attributes of these social parasites have been described, their genetic attributes require more detailed exploration. Here, we investigate the production of mandibular gland pheromones in queenless workers of two sub-species of African honey bees; A. m. scutellata (low reproductive potential) and A. m. capensis clones (high reproductive potential). We used standard techniques in gas chromatography to assess the amounts of various pheromone components present, and qPCR to assess the expression of cytochrome P450 genes cyp6bd1 and cyp6as8, thought to be involved in the caste-dependent hydroxylation of acylated stearic acid in queens and workers, respectively. We found that, for both subspecies, the quality and quantity of the individual pheromone components vary with age, and that from the onset, A. m. capensis parasites make use of gene pathways typically upregulated in queens in achieving reproductive dominance. Due to the high production of 9-hydroxy-decenoic acid (9-HDA) the precursor to the queen substance 9-oxo-decenoic acid (9-ODA) in newly emerged capensis clones, we argue that clones are primed for parasitism upon emergence and develop into fully fledged parasites depending on the colony's social environment.

Effects of larval Age at Grafting and Juvenile Hormone on Morphometry and Reproductive Quality Parameters of in Vitro Reared Honey Bees (Hymenoptera: Apidae)

The honey bee queen plays a central role in the Apis mellifera L. (Hymenoptera: Apidae) colony, and her high reproductive capacity is fundamental for building up the workforce of a colony. Caste development in honey bee females involves elaborate physiological pathways unleashed at the beginning of the first larval instars, with juvenile hormone (JH) playing a crucial role. Here we took advantage of established in vitro rearing techniques to conduct a 2 × 2 experimental design and test initial rearing age (young vs old) and JH treatment (JH III vs solvent control) to enlighten the role of nutrient quality and JH in shaping honey bee female fertility, morphological features related to queenliness, and key physiological parameters (hemolymph vitellogenin/Vg, sugar levels, and Vg transcript levels). Our results show that while the age at initial larval rearing had major impacts on external morphology development, where younger larvae exhibited a higher probability to develop into queen-like adults morphotypes, the JH application during the larval stage improved physiological pathways related to ovary development and metabolism during the ontogenic development. We detected that the supplementation of queen larvae with JH promoted important benefits regarding queen fertility as the increase of ovariole number and vg levels at hemolymph, both crucial factors at eggs production. The data presented here provide guidance in efforts to improve honey bee queen quality, especially in light of frequent episodes of queen failures in the beekeeping industry.

Determination of 10-Hydroxy-2-Decenoic Acid of Royal Jelly Using Near-Infrared Spectroscopy Combined with Chemometrics

A rapid quantitative analysis model for determining the hydroxy-2-decenoic acid (10-HDA) content of royal jelly based on near-infrared spectroscopy combining with PLS has been developed. Firstly, near-infrared spectra of 232 royal jelly samples with different 10-HDA concentrations (0.35% to 2.44%) were be collected. Second-order derivative processing of the spectra was carried out to construct a full-spectrum PLS model. Secondly, GA-PLS, CARS-PLS, and Si-PLS were used to select characteristic wavelengths from the second-order derivative spectrum to construct a PLS calibration model. Finally, 58 samples were used to select the best predictive model for 10-HDA content. The result show that the PLS model constructed after wavelength selection was significantly more accurate than the full spectrum model. The Si-PLS algorithm performed best and the corresponding characteristic wavelength range were: 980 to 1038, 1220 to 1278, 1340 to 1398, and 1688 to 1746 nm. The prediction results were RMSEP = 0.1496% and R_P = 0.9380. Hence, it is feasible to employ near-infrared spectra to analyze 10-HDA in royal jelly.

Honeybee Evolution: Royal Jelly Proteins Help Queen Larvae to Stay on Top

A new study shows that, in honey bees, the main role of certain proteins in royal jelly is to ensure that the larva stays in its cell, thereby allowing it to develop into a queen.

The rise and fall of major royal jelly proteins during a honeybee (Apis mellifera) workers' life

The genome of the western honeybee (Apis mellifera) harbors nine transcribed major royal jelly protein genes (mrjp1-9) which originate from a single-copy precursor via gene duplication. The first MRJP was identified in royal jelly, a secretion of the bees' hypopharyngeal glands that is used by young worker bees, called nurses, to feed developing larvae. Thus, MRJPs are frequently assumed to mainly have functions for developing bee larvae and to be expressed in the food glands of nurse bees. In-depth knowledge on caste- and age-specific role and abundance of MRJPs is missing. We here show, using combined quantitative real-time PCR with quantitative mass spectrometry, that expression and protein amount of mrjp1-5 and mrjp7 show an age-dependent pattern in worker's hypopharyngeal glands as well as in brains, albeit lower relative abundance in brains than in glands. Expression increases after hatching until the nurse bee period and is followed by a decrease in older workers that forage for plant products. Mrjp6 expression deviates considerably from the expression profiles of the other mrjps, does not significantly vary in the brain, and shows its highest expression in the hypopharyngeal glands during the forager period. Furthermore, it is the only mrjp of which transcript abundance does not correlate with protein amount. Mrjp8 and mrjp9 show, compared to the other mrjps, a very low expression in both tissues. Albeit mrjp8 mRNA was detected via qPCR, the protein was not quantified in any of the tissues. Due to the occurrence of MRJP8 and MRJP9 in other body parts of the bees, for example, the venom gland, they might not have a hypopharyngeal gland- or brain-specific function but rather functions in other tissues. Thus, mrjp1-7 but not mrjp8 and mrjp9 might be involved in the regulation of phenotypic plasticity and age polyethism in worker honeybees.

pH-dependent stability of honey bee (Apis mellifera) major royal jelly proteins

Honey bee larval food jelly is a secretion of the hypopharyngeal and mandibular glands of young worker bees that take care of the growing brood in the hive. Food jelly is fed to all larvae (workers, drones and queens) and as royal jelly to the queen bee for her entire life. Up to 18% of the food jelly account for proteins the majority of which belongs to the major royal jelly protein (MRJP) family. These proteins are produced in the hypopharyngeal glands at a pH value of 7.0. Before being fed to the larvae, they are mixed with the fatty acids secreted by the mandibular glands of the worker bees resulting at a pH of 4.0 in the food jelly. Thus, MRJPs are exposed to a broad pH range from their site of synthesis to the actual secreted larval food. We therefore determined the pH-dependent stability of MRJP1, MRJP2 and MRJP3 purified from royal jelly using differential scanning fluorimetry. All MRJPs were much more stable at acidic pH values compared to neutral ones with all proteins showing highest stability at pH 4.0 or 4.5, the native pH of royal jelly.

Transcriptional Control of Honey Bee (Apis mellifera) Major Royal Jelly Proteins by 20-Hydroxyecdysone

One of the first tasks of worker honey bees (Apis mellifera) during their lifetime is to feed the larval offspring. In brief, young workers (nurse bees) secrete a special food jelly that contains a large amount of unique major royal jelly proteins (MRJPs). The regulation of mrjp gene expression is not well understood, but the large upregulation in well-fed nurse bees suggests a tight repression until, or a massive induction upon, hatching of the adult worker bees. The lipoprotein vitellogenin, the synthesis of which is regulated by the two systemic hormones 20-hydroxyecdysone and juvenile hormone, is thought to be a precursor for the production of MRJPs. Thus, the regulation of mrjp expression by the said systemic hormones is likely. This study focusses on the role of 20-hydroxyecdysone by elucidating its effect on mrjp gene expression dynamics. Specifically, we tested whether 20-hydroxyecdysone displayed differential effects on various mrjps. We found that the expression of the mrjps (mrjp1–3) that were finally secreted in large amounts into the food jelly, in particular, were down regulated by 20-hydroxyecdysone treatment, with mrjp3 showing the highest repression value.

Architecture of the native major royal jelly protein 1 oligomer

Honeybee caste development is nutritionally regulated by royal jelly (RJ). Major royal jelly protein 1 (MRJP1), the most abundant glycoprotein among soluble royal jelly proteins, plays pivotal roles in honeybee nutrition and larvae development, and exhibits broad pharmacological activities in humans. However, its structure has long remained unknown. Herein, we identify and report a 16-molecule architecture of native MRJP1 oligomer containing four MRJP1, four apisimin, and eight unanticipated 24-methylenecholesterol molecules at 2.65 Å resolution. MRJP1 has a unique six-bladed β-propeller fold with three disulfide bonds, and it interacts with apisimin mainly by hydrophobic interaction. Every four 24-methylenecholesterol molecules are packaged by two MRJP1 and two apisimin molecules. This assembly dimerizes to form an H-shaped MRJP1₄-apisimin₄-24-methylenecholesterol₈ complex via apisimin in a conserved and pH-dependent fashion. Our findings offer a structural basis for understanding the pharmacological effects of MRJPs and 24-methylenecholesterol, and provide insights into their unique physiological roles in bees.