Worker honeybee brain proteome

Study of Melipona quadrifasciata brain under operant learning using proteomic and phosphoproteomic analysis

Learning to anticipate events based on the predictive relationship between an action and an outcome (operant conditioning) is a form of associative learning shared by humans and most of other living beings, including invertebrates. Several behavioral studies on the mechanisms of operant conditioning have included Melipona quadrifasciata, a honey bee that is easily manipulated due to lack of sting. In this work, brain proteomes of Melipona bees trained using operant conditioning and untrained (control) bees were compared by two-dimensional gel electrophoresis analysis within pI range of 3-10 and 4-7; in order to find proteins specifically related to this type of associative learning.One protein was detected with differential protein abundance in the brains of trained bees, when compared to not trained ones, through computational gel imaging and statistical analysis. This protein was identified by peptide mass fingerprinting and MS/MS peptide fragmentation using a MALDI-TOF/TOF mass spectrometer as one isoform of arginine kinase monomer, apparently dephosphorylated. Brain protein maps were obtained by 2-DE (Two-dimensional gel electrophoresis) from a total proteins and phosphoproteins extract of the bee Melipona quadrifasciata. One isoform of arginine kinase, probably a dephosphorylated isoform, was significantly more abundant in the brain of trained bees using operant conditioning. Arginine kinase has been reported as an important enzyme of the energy releasing process in the visual system of the bee, but it may carry out additional and unexpected functions in the bee brain for learning process.

Single-cell transcriptomic analysis of honeybee brains identifies vitellogenin as caste differentiation-related factor

The honeybee (Apis mellifera) is a well-known eusocial insect. In honeybee colonies, thousands of sterile workers, including nurse and forager bees, perform various tasks within or outside the hive, respectively. The queen is the only fertile female and is responsible for reproduction. The queen and workers share similar genomes but occupy different caste statuses. We established single-cell transcriptomic atlases of brains from queens and worker subcastes and identified five major cell groups: Kenyon, optic lobe, olfactory projection, glial, and hemocyte cells. By dividing Kenyon and glial cells into multiple subtypes based on credible markers, we observed that vitellogenin (vg) was highly expressed in specific glial-cell subtypes in brains of queens. Knockdown of vg at the early larval stage significantly suppressed the development into adult queens. We demonstrate vg expression as a "molecular signature" for the queen caste and suggest involvement of vg in regulating caste differentiation.

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scRNA-seq revealed distinct gene expression in the brains of queens and workers

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Vitellogenin (vg) may represent a "molecular signature" of the queen caste

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Knockdown of vg at early larval stage suppressed development into adult queens

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Vg may be involved in regulating caste differentiation

Using a toxicoproteomic approach to investigate the effects of thiamethoxam into the brain of Apis mellifera

Neonicotinoids have been described as toxic to bees. In this context, the A. mellifera foragers were exposed to a sublethal concentration of thiamethoxam (LC_50/100: 0,0227 ng de thiamethoxam/μL^-1 diet), a neurotoxic insecticide, for 8 days; and it was decided to investigate the insecticide effect on the brain by a shotgun proteomic approach followed by label-free quantitative-based proteomics. A total of 401 proteins were identified in the control group (CG); and a total of 350 proteins in the thiamethoxam exposed group (TMX). Quantitative proteomics data showed up 251 proteins with significant quantitative values in the TMX group. These findings demonstrated the occurrence of shared and unique proteins with altered expression in the TMX group, such as ATP synthase subunit beta, heat shock protein cognate 4, spectrin beta chain-like, mushroom body large-type Kenyon cell-specific protein 1-like, tubulin alpha-1 chain-like, arginine kinase, epidermal growth factor receptor, odorant receptor, glutamine synthetase, glutamate receptor, and cytochrome P450 4c3. Meanwhile, the proteins that were expressed uniquely in the TMX group are involved mainly in the phosphorylation, cellular protein modification, and cell surface receptor signalling processes. Interaction network results showed that identified proteins are present in five different metabolic pathways - oxidative stress, cytoskeleton control, visual process, olfactory memory, and glutamate metabolism. Our scientific outcomes demonstrated that a sublethal concentration of thiamethoxam can impair biological processes and important metabolic pathways, causing damage to the nervous system of bees, and in the long term, can compromise the nutrition and physiology of individuals from the colony.

The Emerging Proteomic Research Facilitates in-Depth Understanding of the Biology of Honeybees

Advances in instrumentation and computational analysis in proteomics have opened new doors for honeybee biological research at the molecular and biochemical levels. Proteomics has greatly expanded the understanding of honeybee biology since its introduction in 2005, through which key signaling pathways and proteins that drive honeybee development and behavioral physiology have been identified. This is critical for downstream mechanistic investigation by knocking a gene down/out or overexpressing it and being able to attribute a specific phenotype/biochemical change to that gene. Here, we review how emerging proteome research has contributed to the new understanding of honeybee biology. A systematic and comprehensive analysis of global scientific progress in honeybee proteome research is essential for a better understanding of research topics and trends, and is potentially useful for future research directions.

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.

The effects of the neonicotinoid imidacloprid on gene expression and DNA methylation in the buff-tailed bumblebee Bombus terrestris

Neonicotinoids are effective insecticides used on many important arable and horticultural crops. They are nicotinic acetylcholine receptor agonists which disrupt the function of insect neurons and cause paralysis and death. In addition to direct mortality, there are numerous sublethal effects of low doses of neonicotinoids on bees. We hypothesize that some of these large array of effects could be a consequence of epigenetic changes in bees induced by neonicotinoids. We compared whole methylome (BS-seq) and RNA-seq libraries of the brains of buff-tailed bumblebee Bombus terrestris workers exposed to field-realistic doses of the neonicotinoid imidacloprid to libraries from control workers. We found numerous genes which show differential expression between neonicotinoid-treated bees and control bees, but no differentially methylated cytosines in any context. We found CpG methylation to be focused mainly in exons and associated with highly expressed genes. We discuss the implications of our results for future legislation.

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.

Combined transcriptome and proteome profiling reveals specific molecular brain signatures for sex, maturation and circalunar clock phase

Many marine animals, ranging from corals to fishes, synchronise reproduction to lunar cycles. In the annelid Platynereis dumerilii, this timing is orchestrated by an endogenous monthly (circalunar) clock entrained by moonlight. Whereas daily (circadian) clocks cause extensive transcriptomic and proteomic changes, the quality and quantity of regulations by circalunar clocks have remained largely elusive. By establishing a combined transcriptomic and proteomic profiling approach, we provide first systematic insight into the molecular changes in Platynereis heads between circalunar phases, and across sexual differentiation and maturation. Whereas maturation elicits large transcriptomic and proteomic changes, the circalunar clock exhibits only minor transcriptomic, but strong proteomic regulation. Our study provides a versatile extraction technique and comprehensive resources. It corroborates that circadian and circalunar clock effects are likely distinct and identifies key molecular brain signatures for reproduction, sex and circalunar clock phase. Examples include prepro-whitnin/proctolin and ependymin-related proteins as circalunar clock targets.

Proteome analysis reveals a strong correlation between olfaction and pollen foraging preference in honeybees

To gain a deeper understanding of the molecular basis of pollen foraging preference, we characterized the proteomes of antennae and brains of bees foraging on pear and rapeseed flowers, and the volatile compounds from nectar, anther, and inflorescence of both plants. Bees foraging on the pollen of the two plants have shaped the distinct proteome arsenals in the antenna and brain to drive olfactory and brain function. In antennae, bees foraging on pear (PA) pollen pathways associated with protein metabolism were induced to synthesize new proteins for modulation of synaptic structures via stabilizing and consolidating specific memory traces. Whereas, bees foraging on rapeseed (BA) pollen pathways implicated in energy metabolism were activated to provide metabolic fuels critical for neural activity. These findings suggest that the distinct biochemical route is functionally enhanced to consolidate the divergent olfaction in PA and BA. In brain, although the uniquely induced pathways in bees forging on both plants are likely to cement selective roles in learning and memory, pollen foraging preference in bees is mainly drived by olfaction. Furthermore, both plants have shaped different repertoires of signal odors and food rewards to attract pollinators. The suggested markers are potentially useful for selection of bees to improve their olfaction for better pollination of the plants.

Antennal Protein Profile in Honeybees: Caste and Task Matter More Than Age

Reproductive and task partitioning in large colonies of social insects suggest that colony members belonging to different castes or performing different tasks during their life (polyethism) may produce specific semiochemicals and be differently sensitive to the variety of pheromones involved in intraspecific chemical communication. The main peripheral olfactory organs are the antennal chemosensilla, where the early olfactory processes take place. At this stage, members of two different families of soluble chemosensory proteins [odorant-binding proteins (OBPs) and chemosensory proteins (CSPs)] show a remarkable affinity for different odorants and act as carriers while a further family, the Niemann-Pick type C2 proteins (NPC2) may have a similar function, although this has not been fully demonstrated. Sensillar lymph also contains Odorant degrading enzymes (ODEs) which are involved in inactivation through degradation of the chemical signals, once the message is conveyed. Despite their importance in chemical communication, little is known about how proteins involved in peripheral olfaction and, more generally antennal proteins, differ in honeybees of different caste, task and age. Here, we investigate for the first time, using a shotgun proteomic approach, the antennal profile of honeybees of different castes (queens and workers) and workers performing different tasks (nurses, guards, and foragers) by controlling for the potential confounding effect of age. Regarding olfactory proteins, major differences were observed between queens and workers, some of which were found to be more abundant in queens (OBP3, OBP18, and NPC2-1) and others to be more abundant in workers (OBP15, OBP21, CSP1, and CSP3); while between workers performing different tasks, OBP14 was more abundant in nurses with respect to guards and foragers. Apart from proteins involved in olfaction, we have found that the antennal proteomes are mainly characterized by castes and tasks, while age has no effect on antennal protein profile. Among the main differences, the strong decrease in vitellogenins found in guards and foragers is not associated with age.

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.

Proteomics Reveals the Molecular Underpinnings of Stronger Learning and Memory in Eastern Compared to Western Bees

The eastern (Apis cerana cerana, Acc) and western (Apis mellifera ligustica, Aml) honeybee are two major honeybee species. Surprisingly, little is known about the fundamental molecular neurobiology of brain suborgans of Acc and Aml. We characterized and compared the proteomes of mushroom bodies (MBs), antennal lobes (ALs) and optical lobes (OLs) in the brain of both species, and biologically validated the functions related to learning and memory. Acc and Aml have evolved similar proteome signatures in MBs and OLs to drive the domain-specific neural activities. In MBs of both species, commonly enriched and enhanced functional groups related to protein metabolism and Ca²⁺ transport relative to ALs and OLs, suggests that proteins and Ca²⁺ are vital for consolidating learning and memory via modulation of synaptic structure and signal transduction. Furthermore, in OLs of both species, the mainly enriched ribonucleoside metabolism suggests its vital role as second messenger in promoting phototransduction. Notably, in ALs of both species, distinct proteome settings have shaped to prime olfactory learning and memory. In ALs of Acc, this is supported by the enriched cytoskeleton organization to sustain olfactory signaling through modulation of plasticity in glomeruli and intracellular transport. In ALs of Aml, however, the enriched functional groups implicated in hydrogen ion transport are indicative of their importance in supporting olfactory processes by regulation of synaptic transmission. The biological confirmation of enhanced activities of protein metabolism and signal transduction in ALs and MBs of Acc relative to in Aml demonstrates that a stronger sense of olfactory learning and memory has evolved in Acc. The reported first in-depth proteome data of honeybee brain suborgans provide a novel insight into the molecular basis of neurobiology, and is potentially useful for further neurological studies in honeybees and other insects.

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.

Mass Spectrometry-Based Approaches to Understand the Molecular Basis of Memory

The central nervous system is responsible for an array of cognitive functions such as memory, learning, language, and attention. These processes tend to take place in distinct brain regions; yet, they need to be integrated to give rise to adaptive or meaningful behavior. Since cognitive processes result from underlying cellular and molecular changes, genomics and transcriptomics assays have been applied to human and animal models to understand such events. Nevertheless, genes and RNAs are not the end products of most biological functions. In order to gain further insights toward the understanding of brain processes, the field of proteomics has been of increasing importance in the past years. Advancements in liquid chromatography-tandem mass spectrometry (LC-MS/MS) have enabled the identification and quantification of thousands of proteins with high accuracy and sensitivity, fostering a revolution in the neurosciences. Herein, we review the molecular bases of explicit memory in the hippocampus. We outline the principles of mass spectrometry (MS)-based proteomics, highlighting the use of this analytical tool to study memory formation. In addition, we discuss MS-based targeted approaches as the future of protein analysis.

PROTEINS OF THE INTEGUMENTARY SYSTEM OF THE HONEYBEE, Apis mellifera

The integument of insects and other arthropods is composed of an inner basal lamina coated by the epidermis, which secretes the bulk of the outer integument layer, the cuticle. The genome sequencing of several insect species has allowed predicting classes of proteins integrating the cuticle. However, only a small proportion of them, as well as other proteins in the integumentary system, have been validated. Using two-dimensional gel electrophoresis coupled with mass spectrometry, we identified 45 different proteins in a total of 112 selected gel spots derived from thoracic integument samples of developing honeybee workers, including 14 cuticular proteins (AmelCPR 3, AmelCPR 12, AmelCPR 16, AmelCPR 27, apidermin 2, apidermin 3, endocuticle structural glycoprotein SgAbd-8-like, LOC100577363, LOC408365, LOC413679, LOC725454, LOC100576916, LOC725838, and peritrophin 3-C analogous). Gene ontology functional analysis revealed that the higher proportions of the identified proteins have molecular functions related to catalytic and structural molecule activities, are involved in metabolic biological processes, and pertain to the protein class of structural or cytoskeletal proteins and hydrolases. It is noteworthy that 26.7% of the identified proteins, including five cuticular proteins, were revealed as protein species resulting from allelic isoforms or derived from posttranslational modifications. Also, 66.7% of the identified cuticular proteins were expressed in more than one developmental phase, thus indicating that they are part of the larval, pupal, and adult cuticle. Our data provide experimental support for predicted honeybee gene products and new information on proteins expressed in the developing integument.

Proteome Analysis of the Hemolymph, Mushroom Body, and Antenna Provides Novel Insight into Honeybee Resistance against Varroa Infestation

Varroa destructor has been identified as a major culprit responsible for the losses of millions of honeybee colonies. Varroa sensitive hygiene (VSH) is a suite of behaviors from adult bees to suppress mite reproduction by uncapping and/or removing mite infested pupae from a sealed brood. Despite the efforts to elucidate the molecular underpinnings of VSH, they remain largely unknown. We investigated the proteome of mushroom bodies (MBs) and antennae of adult bees with and without VSH from a stock selected for VSH based on their response to artificially Varroa-infected brood cells by near-infrared camera observation. The pupal hemolymph proteome was also compared between the VSH-line and the line that was not selected for VSH. The identified 8609 proteins in the hemolymph, MBs, and antennae represent the most depth coverage of the honeybee proteome (>55%) to date. In the hemolymph, the VSH-line adapts a unique strategy to boost the social immunity and drive pupal organogenesis by enhancing energy metabolism and protein biosynthesis. In MBs, the up-regulated proteins implicated in neuronal sensitivity suggest their roles to promote the execution of VSH by activation of synaptic vesicles and calcium channel activities. In antennae, the highly expressed proteins associated with sensitivity of olfactory senses and signal transmissions signify their roles by inputting a strong signal to the MBs for initiating VSH. These observations illustrate that the enhanced social immunities and olfactory and neuronal sensitivity play key roles in the combat against Varroa infestation. The identified candidate markers may be useful for accelerating marker-associated selection for VSH to aid in resistance to a parasite responsible for decline in honeybee health.

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.

The HEX 110 Hexamerin Is a Cytoplasmic and Nucleolar Protein in the Ovaries of Apis mellifera

Hexamerins are insect storage proteins abundantly secreted by the larval fat body into the haemolymph. The canonical role of hexamerins consists of serving as an amino acid reserve for development toward the adult stage. However, in Apis mellifera, immunofluorescence assays coupled to confocal laser-scanning microscopy, and high-throughput sequencing, have recently shown the presence of hexamerins in other organs than the fat body. These findings have led us to study these proteins with the expectation of uncovering additional functions in insect development. We show here that a honeybee hexamerin, HEX 110, localizes in the cytoplasm and nucleus of ovarian cells. In the nucleus of somatic and germline cells, HEX 110 colocalized with a nucleolar protein, fibrillarin, suggesting a structural or even regulatory function in the nucleolus. RNase A provoked the loss of HEX 110 signals in the ovarioles, indicating that the subcellular localization depends on RNA. This was reinforced by incubating ovaries with pyronin Y, a RNA-specific dye. Together, the colocalization with fibrillarin and pyronin Y, and the sensitivity to RNase, highlight unprecedented roles for HEX110 in the nucleolus, the nuclear structure harbouring the gene cluster involved in ribosomal RNA production. However, the similar patterns of HEX 110 foci distribution in the active and inactive ovaries of queens and workers preclude its association with the functional status of these organs.

Shotgun proteomic analysis of Bombyx mori brain: emphasis on regulation of behavior and development of the nervous system

The insect brain plays crucial roles in the regulation of growth and development and in all types of behavior. We used sodium dodecyl sulfate polyacrylamide gel electrophoresis and high-performance liquid chromatography - electron spray ionization tandem mass spectrometry (ESI-MS/MS) shotgun to identify the proteome of the silkworm brain, to investigate its protein composition and to understand their biological functions. A total of 2210 proteins with molecular weights in the range of 5.64-1539.82 kDa and isoelectric points in the range of 3.78-12.55 were identified. These proteins were annotated according to Gene Ontology Annotation into the categories of molecular function, biological process and cellular component. We characterized two categories of proteins: one includes behavior-related proteins involved in the regulation of behaviors, such as locomotion, reproduction and learning; the other consists of proteins related to the development or function of the nervous system. The identified proteins were classified into 283 different pathways according to KEGG analysis, including the PI3K-Akt signaling pathway which plays a crucial role in mediating survival signals in a wide range of neuronal cell types. This extensive protein profile provides a basis for further understanding of the physiological functions in the silkworm brain.

Proteome Analysis Unravels Mechanism Underling the Embryogenesis of the Honeybee Drone and Its Divergence with the Worker (Apis mellifera lingustica)

The worker and drone bees each contain a separate diploid and haploid genetic makeup, respectively. Mechanisms regulating the embryogenesis of the drone and its mechanistic difference with the worker are still poorly understood. The proteomes of the two embryos at three time-points throughout development were analyzed by applying mass spectrometry-based proteomics. We identified 2788 and 2840 proteins in the worker and drone embryos, respectively. The age-dependent proteome driving the drone embryogenesis generally follows the worker's. The two embryos however evolve a distinct proteome setting to prime their respective embryogenesis. The strongly expressed proteins and pathways related to transcriptional-translational machinery and morphogenesis at 24 h drone embryo relative to the worker, illustrating the earlier occurrence of morphogenesis in the drone than worker. These morphogenesis differences remain through to the middle-late stage in the two embryos. The two embryos employ distinct antioxidant mechanisms coinciding with the temporal-difference organogenesis. The drone embryo's strongly expressed cytoskeletal proteins signify key roles to match its large body size. The RNAi induced knockdown of the ribosomal protein offers evidence for the functional investigation of gene regulating of honeybee embryogenesis. The data significantly expand novel regulatory mechanisms governing the embryogenesis, which is potentially important for honeybee and other insects.

Analysis of protein composition using multidimensional chromatography and mass spectrometry

Multidimensional liquid chromatography of peptides produced by protease digestion of complex protein mixtures followed by tandem mass spectrometry can be coupled with automated database searching to identify large numbers of proteins in complex samples. These methods avoid the limitations of gel electrophoresis and in-gel digestions by directly identifying protein mixtures in solution. One method used extensively is named Multidimensional Protein Identification Technology (MudPIT), where reversed-phase chromatography and strong cation-exchange chromatography are coupled directly in a microcapillary column. This column is then placed in line between an HPLC and a mass spectrometer for complex mixture analysis. MudPIT remains a powerful approach for analyzing complex mixtures like whole proteomes and protein complexes. MudPIT is used for quantitative proteomic analysis of complex mixtures to generate novel biological insights.

Modification of the brain proteome of Africanized honeybees (Apis mellifera) exposed to a sub-lethal doses of the insecticide fipronil

Fipronil is a phenylpyrazole insecticide that is widely used in Brazilian agriculture for pest control. Although honeybees are not targets of fipronil, studies indicate that this pesticide can be harmful to honeybees. To assess the effects of fipronil in the brain of Africanized Apis mellifera workers, this study focused on the toxico-proteome profiling of the brain of newly emerged and aged honeybee workers that were exposed to a sub-lethal dose (10 pg fipronil per day. i.e. (1)/100 of LD50/bee/day during 5 days) of the insecticide. Proteomic analysis identified 25 proteins that were differentially up-regulated or down-regulated when the fipronil-exposed and non-exposed groups were compared. These proteins are potentially related to pathogen susceptibility, neuronal chemical stress, neuronal protein misfolding, and occurrence of apoptosis, ischemia, visual impairment, damaged synapse formation, brain degeneration, memory and learning impairment. The exposure of honeybees to a very low dose of fipronil, even for a short period of time (5 days), was sufficient to cause a series of important neuroproteomic changes in the brains of honeybees.

Brain proteomics of Anopheles gambiae

Anopheles gambiae has a well-adapted system for host localization, feeding, and mating behavior, which are all governed by neuronal processes in the brain. However, there are no published reports characterizing the brain proteome to elucidate neuronal signaling mechanisms in the vector. To this end, a large-scale mapping of the brain proteome of An. gambiae was carried out using high resolution tandem mass spectrometry, revealing a repertoire of >1800 proteins, of which 15% could not be assigned any function. A large proportion of the identified proteins were predicted to be involved in diverse biological processes including metabolism, transport, protein synthesis, and olfaction. This study also led to the identification of 10 GPCR classes of proteins, which could govern sensory pathways in mosquitoes. Proteins involved in metabolic and neural processes, chromatin modeling, and synaptic vesicle transport associated with neuronal transmission were predominantly expressed in the brain. Proteogenomic analysis expanded our findings with the identification of 15 novel genes and 71 cases of gene refinements, a subset of which were validated by RT-PCR and sequencing. Overall, our study offers valuable insights into the brain physiology of the vector that could possibly open avenues for intervention strategies for malaria in the future.

In-depth proteomics characterization of embryogenesis of the honey bee worker (Apis mellifera ligustica)

Identifying proteome changes of honey bee embryogenesis is of prime importance for unraveling the molecular mechanisms that they underlie. However, many proteomic changes during the embryonic period are not well characterized. We analyzed the proteomic alterations over the complete time course of honey bee worker embryogenesis at 24, 48, and 72 h of age, using mass spectrometry-based proteomics, label-free quantitation, and bioinformatics. Of the 1460 proteins identified the embryo of all three ages, the core proteome (proteins shared by the embryos of all three ages, accounting for 40%) was mainly involved in protein synthesis, metabolic energy, development, and molecular transporter, which indicates their centrality in driving embryogenesis. However, embryos at different developmental stages have their own specific proteome and pathway signatures to coordinate and modulate developmental events. The young embryos (<24 h) stronger expression of proteins related to nutrition storage and nucleic acid metabolism may correlate with the cell proliferation occurring at this stage. The middle aged embryos (24-48 h) enhanced expression of proteins associated with cell cycle control, transporters, antioxidant activity, and the cytoskeleton suggest their roles to support rudimentary organogenesis. Among these proteins, the biological pathways of aminoacyl-tRNA biosynthesis, β-alanine metabolism, and protein export are intensively activated in the embryos of middle age. The old embryos (48-72 h) elevated expression of proteins implicated in fatty acid metabolism and morphogenesis indicate their functionality for the formation and development of organs and dorsal closure, in which the biological pathways of fatty acid metabolism and RNA transport are highly activated. These findings add novel understanding to the molecular details of honey bee embryogenesis, in which the programmed activation of the proteome matches with the physiological transition observed during embryogenesis. The identified biological pathways and key node proteins allow for further functional analysis and genetic manipulation for both the honey bee embryos and other eusocial insects.

Royal jelly-like protein localization reveals differences in hypopharyngeal glands buildup and conserved expression pattern in brains of bumblebees and honeybees

Royal jelly proteins (MRJPs) of the honeybee bear several open questions. One of them is their expression in tissues other than the hypopharyngeal glands (HGs), the site of royal jelly production. The sole MRJP-like gene of the bumblebee, Bombus terrestris (BtRJPL), represents a pre-diversification stage of the MRJP gene evolution in bees. Here we investigate the expression of BtRJPL in the HGs and the brain of bumblebees. Comparison of the HGs of bumblebees and honeybees revealed striking differences in their morphology with respect to sex- and caste-specific appearance, number of cells per acinus, and filamentous actin (F-actin) rings. At the cellular level, we found a temporary F-actin-covered meshwork in the secretory cells, which suggests a role for actin in the biogenesis of the end apparatus in HGs. Using immunohistochemical localization, we show that BtRJPL is expressed in the bumblebee brain, predominantly in the Kenyon cells of the mushroom bodies, the site of sensory integration in insects, and in the optic lobes. Our data suggest that a dual gland-brain function preceded the multiplication of MRJPs in the honeybee lineage. In the course of the honeybee evolution, HGs dramatically changed their morphology in order to serve a food-producing function.

More than royal food - Major royal jelly protein genes in sexuals and workers of the honeybee Apis mellifera

Background

In the honeybee Apis mellifera, female larvae destined to become a queen are fed with royal jelly, a secretion of the hypopharyngeal glands of young nurse bees that rear the brood. The protein moiety of royal jelly comprises mostly major royal jelly proteins (MRJPs) of which the coding genes (mrjp1-9) have been identified on chromosome 11 in the honeybee’s genome.

Results

We determined the expression of mrjp1-9 among the honeybee worker caste (nurses, foragers) and the sexuals (queens (unmated, mated) and drones) in various body parts (head, thorax, abdomen). Specific mrjp expression was not only found in brood rearing nurse bees, but also in foragers and the sexuals.

Conclusions

The expression of mrjp1 to 7 is characteristic for the heads of worker bees, with an elevated expression of mrjp1-4 and 7 in nurse bees compared to foragers. Mrjp5 and 6 were higher in foragers compared to nurses suggesting functions in addition to those of brood food proteins. Furthermore, the expression of mrjp9 was high in the heads, thoraces and abdomen of almost all female bees, suggesting a function irrespective of body section. This completely different expression profile suggests mrjp9 to code for the most ancestral major royal jelly protein of the honeybee.

A comparison of digital gene expression profiling and methyl DNA immunoprecipitation as methods for gene discovery in honeybee (Apis mellifera) behavioural genomic analyses

The honey bee has a well-organized system of division of labour among workers. Workers typically progress through a series of discrete behavioural castes as they age, and this has become an important case study for exploring how dynamic changes in gene expression can influence behaviour. Here we applied both digital gene expression analysis and methyl DNA immunoprecipitation analysis to nurse, forager and reverted nurse bees (nurses that have returned to the nursing state after a period spent foraging) from the same colony in order to compare the outcomes of these different forms of genomic analysis. A total of 874 and 710 significantly differentially expressed genes were identified in forager/nurse and reverted nurse/forager comparisons respectively. Of these, 229 genes exhibited reversed directions of gene expression differences between the forager/nurse and reverted nurse/forager comparisons. Using methyl-DNA immunoprecipitation combined with high-throughput sequencing (MeDIP-seq) we identified 366 and 442 significantly differentially methylated genes in forager/nurse and reverted nurse/forager comparisons respectively. Of these, 165 genes were identified as differentially methylated in both comparisons. However, very few genes were identified as both differentially expressed and differentially methylated in our comparisons of nurses and foragers. These findings confirm that changes in both gene expression and DNA methylation are involved in the nurse and forager behavioural castes, but the different analytical methods reveal quite distinct sets of candidate genes.