Proteomics analysis reveals protein expression differences for hypopharyngeal gland activity in the honeybee, Apis mellifera carnica Pollmann

The Composition of Fatty Acids in Bee Pollen, Royal Jelly, Buckthorn Oil and Their Mixtures with Pollen Preserved for Storage

Honey produced by A. mellifera contains minor components present in the nectar collected from plants. Various studies of honey components and all other bee products can be informative in assessing their quality. The aim of the present study was to determine the content and composition of fatty acids (FAs) in sea buckthorn oil (SBO), royal jelly (RJ) and bee pollen (BP) and the changes in FAs content in these products during storage. The diversity of FAs and the effect of storage time on FAs content was also evaluated for the prepared-for-preservation mixtures, which included the following samples: pollen mixed with honey at a ratio of 1:2 (w/w); sample BPH, a well; BPH + 1% (w/w) SBO; and BPH + 1% (w/w) SBO + 2% (w/w) RJ. Fresh bee-collected pollen and RJ were stored at -20 °C, whereas the conserved samples were stored at +4 °C in hermetically sealed jars. The data revealed that RJ demonstrated the highest diversity of fatty acids compared to BP and BP prepared for storage with honey along with SBO and RJ. Palmitic and stearic acids were found in the highest amounts out of the eight saturated fatty acids identified in the studied SBO and RJ. The amount of these fatty acids in RJ compared to SBO was 1.27 and 6.14 times higher, respectively. In total, twenty-two unsaturated fatty acids (USFA) were identified in RJ and fourteen were found in SBO. The SBO used in this study was found to be high in linoleic acid, resulting in an increased n-6 fatty acids ratio in the prepared samples. Essential fatty acids eicosapentaenoic (EPA) and docosahexaenoic (DHA) were found in RJ, as well as in BP and BP mixed with honey. These FAs were not identified in the samples prepared with SBO even in the sample supplemented with RJ. The highest decrease in docosadienoic fatty acid was found in the BPH sample compared to BP, while arachidonic acid mostly decreased in BPH + 1% SBO compared to the BPH + 1% (w/w) SBO + 2% (w/w) RJ samples stored at +4 °C. Bee-collected pollen had the greatest influence on the number of FAs in its mixture with honey.

Decoupling the effects of nutrition, age, and behavioral caste on honey bee physiology, immunity, and colony health

Nutritional stress, especially a dearth of pollen, has been linked to honey bee colony losses. Colony-level experiments are critical for understanding the mechanisms by which nutritional stress affects individual honey bee physiology and pushes honey bee colonies to collapse. In this study, we investigated the impact of pollen restriction on key markers of honey bee physiology, main elements of the immune system, and predominant honey bee viruses. To achieve this objective, we uncoupled the effects of behavior, age, and nutritional conditions using a new colony establishment technique designed to control size, demography, and genetic background. Our results showed that the expression of storage proteins, including vitellogenin (vg) and royal jelly major protein 1 (mrjp1), were significantly associated with nursing, pollen ingestion, and older age. On the other hand, genes involved in hormonal regulation including insulin-like peptides (ilp1 and ilp2) and methyl farnesoate epoxidase (mfe), exhibited higher expression levels in young foragers from colonies not experiencing pollen restriction. In contrast, pollen restriction induced higher levels of insulin-like peptides in old nurses. On the other hand, we found a strong effect of behavior on the expression of all immune genes, with higher expression levels in foragers. In contrast, the effects of nutrition and age were significant only the expression of the regulatory gene dorsal. We also found multiple interactions of the experimental variables on viral titers, including higher Deformed wing virus (DWV) titers associated with foraging and age-related decline. In addition, nutrition significantly affected DWV titers in young nurses, with higher titers induced by pollen ingestion. In contrast, higher levels of Black queen cell virus (BQCV) were associated with pollen restriction. Finally, correlation, PCA, and NMDS analyses proved that behavior had had the strongest effect on gene expression and viral titers, followed by age and nutrition. These analyses also support multiple interactions among genes and virus analyzed, including negative correlations between the expression of genes encoding storage proteins associated with pollen ingestion and nursing (vg and mrjp1) with the expression of immune genes and DWV titers. Our results provide new insights into the proximal mechanisms by which nutritional stress is associated with changes in honey bee physiology, immunity, and viral titers.

The metabolic pathways of polyhydroxyalkanoates and exopolysaccharides synthesized by Haloferax mediterranei in response to elevated salinity

How polymer synthesis is mobilized or activated as a biological response of Haloferax mediterranei against hypertonic conditions remains largely unexplored. This study investigated the protein expression of H. mediterranei in response to high salinity by using isobaric tags for relative and absolute quantitation (iTRAQ)-based proteomic analysis. The microbes were harvested at end of fermentation at the NaCl salinity of 75 and 250 g L^-1. Among the identified 2123 proteins, 170 proteins were differentially expressed. Gene ontology annotation revealed that the highest number of proteins was annotated in biological process category, which was responsible for metabolic process, cellular component and catalytic activity. Differentially expressed proteins were belonged to the class of response to stimulus as well as catalytic activity and binding. Under high salinity conditions, three pathways were established as key responses of PHA and EPS production to hypertonic pressure. Two overexpressed proteins, beta-ketoacyl-ACP reductase and 3-hydroxyacyl-CoA dehydrogenase, enhanced the synthesis of PHAs. The serine-pyruvate transaminase and serine-glyoxylate transaminase were upregulated, thereby increasing the conversion of glucose to PHA. Downregulated levels of sulfate-adenylyl transferase and adenylyl-sulfate kinase could cause diminished EPS synthesis. This study could contribute to better understanding of the proteomic mechanisms of the synthesized polymers in defending against salt stress. SIGNIFICANCE: Haloferax mediterranei, a family member of halophilic archaea, is well known for its fermentative production of poly-β-hydroxyalkanoates (PHAs). PHAs are natural polymers that exhibit great potential in a wide range of applications such as a good alternative to petroleum-based plastics and the biocompatible material. For decades, the functional role of PHAs synthesized by H. mediterranei is deemed to be carbon and energy reservations. The finding proved that differential production of PHA and EPS in H. mediterranei exposed to elevated salinity was caused by differential protein expression. This is the first report on how PHA and EPS synthesized by H. mediterranei is mobilized as the response of increased salinity, contributing to the understanding of halophilic archaea's response to hypertonic stress and the precise control of fermentation production. Despite its advantages as a PHA cell factory, H. mediterranei synthesized EPS simultaneously, thereby lowering the maximum yield of PHA production. Overall, salinity can be used as a vital microbial fermentation parameter to obtain the highest harvest of PHA, as well as the lowest EPS synthesis in industrial fermentation.

Comparative iTRAQ proteomic profiling of proteins associated with the adaptation of brown planthopper to moderately resistant vs. susceptible rice varieties

The brown planthopper (BPH), Nilaparvata lugens (Stål), is a destructive pest that poses a significant threat to rice plants worldwide. To explore how BPHs adapt to the resistant rice variety, we analyzed proteomics profiles of two virulent N. lugens populations. We focused on Biotype Y, which can survive on the moderately resistant rice variety YHY15, and Biotype I, which can survive on the susceptible rice variety TN1. We performed protein quantitation using the isobaric tag for relative and absolute quantification (iTRAQ) and then compared the expression patterns between two virulent N. lugens populations and found 258 differentially expressed proteins (DEPs). We found that 151 of the DEPs were up-regulated, while 107 were down-regulated. We evaluated transcript levels of 8 expressed genes from the iTRAQ results by qRT-PCR, which revealed transcriptional changes that were consistent with the changes at the protein level. The determination of the protein changes in two virulent N. lugens populations would help to better understanding BPH adaptation to resistant rice varieties and facilitate the better design of new control strategies for host defense against BPH.

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.

In-depth Proteome of the Hypopharyngeal Glands of Honeybee Workers Reveals Highly Activated Protein and Energy Metabolism in Priming the Secretion of Royal Jelly

Royal jelly (RJ) is a secretion of the hypopharyngeal glands (HGs) of honeybee workers. High royal jelly producing bees (RJBs), a stock of honeybees selected from Italian bees (ITBs), have developed a stronger ability to produce RJ than ITBs. However, the mechanism underpinning the high RJ-producing performance in RJBs is still poorly understood. We have comprehensively characterized and compared the proteome across the life span of worker bees between the ITBs and RJBs. Our data uncover distinct molecular landscapes that regulate the gland ontogeny and activity corresponding with age-specific tasks. Nurse bees (NBs) have a well-developed acini morphology and cytoskeleton of secretory cells in HGs to prime the gland activities of RJ secretion. In RJB NBs, pathways involved in protein synthesis and energy metabolism are functionally induced to cement the enhanced RJ secretion compared with ITBs. In behavior-manipulated RJB NBs, the strongly expressed proteins implicated in protein synthesis and energy metabolism further demonstrate their critical roles in the regulation of RJ secretion. Our findings provide a novel understanding of the mechanism consolidating the high RJ-output in RJBs.

Lenalidomide regulates osteocytes fate and related osteoclastogenesis via IL-1β/NF-κB/RANKL signaling

Osteolytic diseases are closely associated with osteocyte fate, indicating a more efficient and crucial role of osteocyte-targeting strategy in inhibiting osteoclastogenesis. Here, we investigated the effects of lenalidomide (Lena) on osteocyte fate in order to regulate osteoclastogenesis via effective cascade-controlling response. Our data revealed that lenalidomide treatment notably rescued IL-1β induced loss of osteocyte viability by inhibiting osteocyte apoptosis with decreased osteoclast-related factors, RANKL and Sclerostin, as demonstrated by the restricted osteoclast formation and reduced bone resorption. Additionally, iTRAQ assay revealed that IL-1β induced activation of NF-κB inhibitor α/β were remarkably downregulated by lenalidomide, showing that lenalidomide impaired NF-κB signaling in osteocytes for inhibiting the expression of osteoclast specific genes in osteoclasts, which was further confirmed by KEGG pathway analysis and Western blot. More interestingly, the in vivo analysis of osteocyte apoptosis and osteoclastogenesis in osteoarthritis mice model indicated a role of lenalidomide in the regulation of osteocyte fate and the consequent inhibition of RANKL-induced osteoclastogenesis. Together, these results suggest that lenalidomide regulates osteocyte fate by attenuating IL-1β/NF-κB signaling, thereby inhibiting RANKL expression for the attenuated osteoclastogenesis both in vitro and vivo, indicating a more efficient remedy among future anti-osteoclastogenesis approaches.

Proteomics Improves the New Understanding of Honeybee Biology

The honeybee is one of the most valuable insect pollinators, playing a key role in pollinating wild vegetation and agricultural crops, with significant contribution to the world's food production. Although honeybees have long been studied as model for social evolution, honeybee biology at the molecular level remained poorly understood until the year 2006. With the availability of the honeybee genome sequence and technological advancements in protein separation, mass spectrometry, and bioinformatics, aspects of honeybee biology such as developmental biology, physiology, behavior, neurobiology, and immunology have been explored to new depths at molecular and biochemical levels. This Review comprehensively summarizes the recent progress in honeybee biology using proteomics to study developmental physiology, task transition, and physiological changes in some of the organs, tissues, and cells based on achievements from the authors' laboratory in this field. The research advances of honeybee proteomics provide new insights for understanding of honeybee biology and future research directions.

Shotgun proteomics deciphered age/division of labor-related functional specification of three honeybee (Apis mellifera L.) exocrine glands

The honeybee (Apis mellifera L.) uses various chemical signals produced by the worker exocrine glands to maintain the functioning of its colony. The roles of worker postcerebral glands (PcGs), thoracic glands (TGs), and mandibular glands (MGs) and the functional changes they undergo according to the division of labor from nursing to foraging are not as well studied. To comprehensively characterize the molecular roles of these glands in workers and their changes according to the division of labor of workers, we analyzed the proteomes of PcGs, TGs, and MGs from nurse bees and foragers using shotgun proteomics technology. We identified approximately 2000 proteins from each of the nurse bee or forager glands and highlighted the features of these glands at the molecular level by semiquantitative enrichment analyses of frequently detected, gland-selective, and labor-selective proteins. First, we found the high potential to produce lipids in PcGs and MGs, suggesting their relation to pheromone production. Second, we also found the proton pumps abundant in TGs and propose some transporters possibly related to the saliva production. Finally, our data unveiled candidate enzymes involved in labor-dependent acid production in MGs.

Identification of genes related to high royal jelly production in the honey bee (Apis mellifera) using microarray analysis

China is the largest royal jelly producer and exporter in the world, and high royal jelly-yielding strains have been bred in the country for approximately three decades. However, information on the molecular mechanism underlying high royal jelly production is scarce. Here, a cDNA microarray was used to screen and identify differentially expressed genes (DEGs) to obtain an overview on the changes in gene expression levels between high and low royal jelly producing bees. We developed a honey bee gene chip that covered 11,689 genes, and this chip was hybridised with cDNA generated from RNA isolated from heads of nursing bees. A total of 369 DEGs were identified between high and low royal jelly producing bees. Amongst these DEGs, 201 (54.47%) genes were up-regulated, whereas 168 (45.53%) were down-regulated in high royal jelly-yielding bees. Gene ontology (GO) analyses showed that they are mainly involved in four key biological processes, and pathway analyses revealed that they belong to a total of 46 biological pathways. These results provide a genetic basis for further studies on the molecular mechanisms involved in high royal jelly production.

Phosphoproteome Analysis Reveals Phosphorylation Underpinnings in the Brains of Nurse and Forager Honeybees (Apis mellifera)

The honeybee brain is a central organ in regulating wide ranges of honeybee biology, including life transition from nurse to forager bees. Knowledge is still lacking on how protein phosphorylation governs the neural activity to drive the age-specific labor division. The cerebral phosphoproteome of nurse and forager honeybees was characterized using Ti⁴⁺-IMAC phosphopeptide enrichment mass-spectrometry-based proteomics and protein kinases (PKs) were predicted. There were 3,077 phosphosites residing on 3,234 phosphopeptides from 1004 phosphoproteins in the nurse bees. For foragers the numbers were 3,056, 3,110, and 958, respectively. Notably, among the total 231 PKs in honeybee proteome, 179 novel PKs were predicted in the honeybee brain, of which 88 were experimentally identified. Proteins involved in wide scenarios of pathways were phosphorylated depending on age: glycolysis/gluconeogenesis, AGE/RAGE and phosphorylation in nurse bees and metal ion transport, ATP metabolic process and phototransduction in forager bees. These observations suggest that phosphorylation is vital to the tuning of protein activity to regulate cerebral function according to the biological duties as nursing and foraging bees. The data provides valuable information on phosphorylation signaling in the honeybee brain and potentially useful resource to understand the signaling mechanism in honeybee neurobiology and in other social insects as well.

Social regulation of ageing by young workers in the honey bee, Apis mellifera

Organisms' lifespans are modulated by both genetic and environmental factors. The lifespan of eusocial insects is determined by features of the division of labor, which itself is influenced by social regulatory mechanisms. In the honey bee, Apis mellifera, the presence of brood and of old workers carrying out foraging tasks are important social drivers of ageing, but the influence of young adult workers is unknown, as it has not been experimentally teased apart from that of brood. In this study, we test the role of young workers in the ageing of their nestmates. We measured the impact of different social contexts characterized by the absence of brood and/or young adults on the lifespan of worker nestmates in field colonies. To acquire insight into the physiological processes occurring under these contexts, we analyzed the expression of genes known to affect honey bee ageing. The data showed that young workers significantly reduced the lifespan of nestmate workers, similar to the effect of brood on its own. Differential expression of vitellogenin, major royal jelly protein-1, and methylase transferase, but not methyl farneosate epoxidase genes suggests that young workers and brood influence ageing of adult nestmate workers via different physiological pathways. We identify young workers as an essential part of the social regulation of ageing in honey bee colonies.

Whole-genome resequencing of honeybee drones to detect genomic selection in a population managed for royal jelly

Four main evolutionary lineages of A. mellifera have been described including eastern Europe (C) and western and northern Europe (M). Many apiculturists prefer bees from the C lineage due to their docility and high productivity. In France, the routine importation of bees from the C lineage has resulted in the widespread admixture of bees from the M lineage. The haplodiploid nature of the honeybee Apis mellifera, and its small genome size, permits affordable and extensive genomics studies. As a pilot study of a larger project to characterise French honeybee populations, we sequenced 60 drones sampled from two commercial populations managed for the production of honey and royal jelly. Results indicate a C lineage origin, whilst mitochondrial analysis suggests two drones originated from the O lineage. Analysis of heterozygous SNPs identified potential copy number variants near to genes encoding odorant binding proteins and several cytochrome P450 genes. Signatures of selection were detected using the hapFLK haplotype-based method, revealing several regions under putative selection for royal jelly production. The framework developed during this study will be applied to a broader sampling regime, allowing the genetic diversity of French honeybees to be characterised in detail.