Changes in protein expression during honey bee larval development

Molecular mechanisms of cis-oxygen bridge neonicotinoids to Apis mellifera Linnaeus chemosensory protein: Surface plasmon resonance, multiple spectroscopy techniques, and molecular modeling

Honeybees, essential pollinators for maintaining biodiversity, are experiencing a sharp population decline, which has become a pressing environmental concern. Among the factors implicated in this decline, neonicotinoid pesticides, particularly those belonging to the fourth generation, have been the focus of extensive scrutiny due to their potential risks to honeybees. This study investigates the molecular basis of these risks by examining the binding interactions between Apis mellifera L. chemosensory protein 3 (AmelCSP3) and neonicotinoids with a cis-oxygen bridge heterocyclic structure. Employing surface plasmon resonance (SPR) in conjunction with multispectral techniques and molecular modeling, this study meticulously analyzed the binding affinity, specificity, and kinetics under conditions that simulate real-world exposure scenarios. Key parameters such as the number of binding sites (n), binding constants (Ka), dissociation constants (KD), and binding distances (r) were quantitatively assessed. The findings revealed that hydrogen bonding and hydrophobic interactions serve as the primary forces driving the binding process, with fluorescence quenching mechanisms involving both dynamic and static interactions. Molecular docking and dynamics simulations further illustrated the stability of these interactions within the active site of the protein. Of particular interest, cis-structured neonicotinoids demonstrated distinct binding characteristics compared to their trans-structured counterparts, including an inverse relationship between the binding constant and temperature. These findings offer critical insights for the design of cis-structured neonicotinoid compounds that are safer for pollinators, thus reducing the impact on non-target organisms such as bees. Furthermore, this research enhances the understanding of the interaction mechanisms between cis-structured neonicotinoid substances and honeybee proteins, providing a foundation for future studies on the environmental safety of these compounds.

Insights into the nutritional value of honeybee drone larvae (Apis mellifera) through proteomic profiling

There is a growing interest and demand for insect-based foods. Edible insects are rich in protein and other nutrients, making them valuable in the daily diet. However, their composition is not yet fully characterised. Therefore, this study aimed to analyse for the first time the qualitative proteome of honeybee (Apis mellifera) drone larvae using sophisticated sample preparation techniques and mass spectrometry. A total of 109 proteins were identified in the larvae. Of these, the largest plurality (38%) were enzymes. In addition, we identified proteins considered to be allergens - the cause of potentially dangerous effects after insect consumption. The results of the analyses may suggest that honeybee larvae are a protein-rich product, with over 100 unique proteins identified based on 1080 peptides. Enzymes indicate intensive development of the larvae. However, as well as nutritious compounds, honeybee larvae contain dangerous allergens. The composition of bee larvae needs to be further tested to make them safe for consumption.

Effect of Rearing in Small-Cell Combs on Activities of Catalase and Superoxide Dismutase and Total Antioxidant Capacity in the Hemolymph of Apis mellifera Workers

Honeybee nests constructed without man-made wax foundation have significantly more variability of cell widths/sizes than those in commercially-kept colonies. The effects of this natural variability in comb cell widths on individual and colony traits have not been explained to date. The investigation of this problem can lead to new findings about the biology, physiology, and possibly, the evolution of the honeybee. The aim of the study was to compare the catalase and superoxide dismutase activities and the total antioxidant capacity levels in the hemolymph of honeybee workers reared in small-cell combs and standard-cell combs in colonies kept simultaneously on standard- and small-cell combs. The ratio of the small-cell combs to the standard-cell combs in the nest was 1:1. The workers reared in small-cell combs were characterized by higher antioxidant activities in the hemolymph than those reared in standard-cell combs. Consequently, their hemolymph had a greater antioxidant capacity, which indicates that they may be better predisposed to be foragers than workers reared in standard-cell combs. To describe the physiological differences between worker bees reared in small- and standard-cell combs in the same colony, the role of the considerable variation in the cell width in natural combs built without the use of artificially produced wax foundation is worth elucidating. The comparison of the apiary and cage experiments indicated that changes in antioxidant activities predominantly result from worker activities, especially those requiring the intensification of metabolism, rather than the age of the worker bees. To reduce the impact on the results of random environmental factors potentially present in one-season studies of honeybee research, investigations should preferably be carried out over a few consecutive years.

Unraveling the Bombus terrestris Hemolymph, an Indicator of the Immune Response to Microbial Infections, through Complementary Mass Spectrometry Approaches

Pollinators, including Bombus terrestris, are crucial for maintaining biodiversity in ecosystems and for agriculture. Deciphering their immune response under stress conditions is a key issue for protecting these populations. To assess this metric, we analyzed the B. terrestris hemolymph as an indicator of their immune status. Hemolymph analysis was carried out using mass spectrometry, MALDI molecular mass fingerprinting was used for its effectiveness in assessing the immune status, and high-resolution mass spectrometry was used to measure the impact of experimental bacterial infections on the "hemoproteome". By infecting with three different types of bacteria, we observed that B. terrestris reacts in a specific way to bacterial attacks. Indeed, bacteria impact survival and stimulate an immune response in infected individuals, visible through changes in the molecular composition of their hemolymph. The characterization and label-free quantification of proteins involved in specific signaling pathways in bumble bees by bottom-up proteomics revealed differences in protein expression between the non-experimentally infected and the infected bees. Our results highlight the alteration of pathways involved in immune and defense reactions, stress, and energetic metabolism. Lastly, we developed molecular signatures reflecting the health status of B. terrestris to pave the way for diagnosis/prognosis tools in response to environmental stress.

In the battle of the disease: a transcriptomic analysis of European foulbrood-diseased larvae of the Western honey bee (Apis mellifera)

BACKGROUND

European foulbrood is a significant bacterial brood disease of Apis sp. and can cause severe and devastating damages in beekeeping operations. Nevertheless, the epidemiology of its causative agent Melissococcus plutonius has been begun to uncover but the underlying mechanisms of infection and cause of disease still is not well understood. Here, we sought to provide insight into the infection mechanism of EFB employing RNAseq in in vitro reared Apis mellifera larvae of two developmental stages to trace transcriptional changes in the course of the disease, including Paenibacillus alvei secondary infected individuals.

RESULTS

In consideration of the progressing development of the larva, we show that infected individuals incur a shift in metabolic and structural protein-encoding genes, which are involved in metabolism of crucial compounds including all branches of macronutrient metabolism, transport protein genes and most strikingly chitin and cuticle associated genes. These changes underpin the frequently observed developmental retardation in EFB disease. Further, sets of expressed genes markedly differ in different stages of infection with almost no overlap. In an earlier stage of infection, a group of regulators of the melanization response cascade and complement component-like genes, predominantly C-type lectin genes, are up-regulated while a differential expression of immune effector genes is completely missing. In contrast, late-stage infected larvae up-regulated the expression of antimicrobial peptides, lysozymes and prominent bacteria-binding haemocyte receptor genes compared to controls. While we clearly show a significant effect of infection on expressed genes, these changes may partly result from a shift in expression timing due to developmental alterations of infection. A secondary infection with P. alvei elicits a specific response with most of the M. plutonius associated differential immune effector gene expression missing and several immune pathway genes even down-regulated.

CONCLUSION

We conclude that with progressing infection diseased individuals undergo a systemic response with a change of metabolism and their activated immune defence repertoire. Moreover, larvae are capable of adjusting their response to a secondary invasion in late stage infections.

Effect of Comb Cell Width on the Activity of the Proteolytic System in the Hemolymph of Apis mellifera Workers

Simple Summary

Honeybees are threatened by many biotic factors, e.g., microbes and parasites such as Nosema spp. and Varroa mites, or predators, as well as environmental factors such as weather conditions, pesticides, or food contaminants. Honeybee colonies have behavioral defense mechanisms against pathogens resulting from their social lifestyle. Moreover, these insects have innate immune barriers. One of the immune defense elements is the proteolytic system consisting of proteases and their inhibitors in the hemolymph (insect blood) and on the body surface. The proteolytic system is activated by both external and internal environmental factors. An important element of the nest environment is the comb. In feral bee colony nests, the bee comb cell size varies in width. In turn, bee colonies in Europe tend to be kept only on standard- (cell width approx. 5.50 mm) or small-cell (cell width approx. 4.90 mm) combs. We assessed the proteolytic system activity in the hemolymph of workers reared in a small-cell comb and a standard-cell comb in colonies kept simultaneously on standard- and small-cell combs. Simultaneous keeping of a colony on standard- and small-cell combs is a novel approach to the use of small-cell combs in beekeeping. The width of comb cells (small or standard) where workers were reared had a significant effect on the protein concentrations and the activities of proteases and protease inhibitors in hemolymph of workers. The protein concentrations in 1-day-old workers were higher in bees reared in small-cell combs than in those reared in standard-cell combs. The opposite was found in the groups of older bees (aged 7, 14 and 21 d). Moreover, the activities of proteases and their inhibitors in 1-day-old workers were always higher in bees reared in standard-cell combs, whereas opposite results were usually obtained in the group of the older workers. The differences between workers reared in the small-cell combs and those from the standard-cell combs may be associated with their different tasks. Workers reared in small-cell combs probably work outside the nest as foragers, whereas those reared in standard-cell combs work in the nest. However, this assumption requires confirmation.

Abstract

This study is a continuation of the innovative research of the impact of rearing of bee colonies simultaneously on standard- and small-cell combs on the traits of worker bees and bee colonies. Its aim was to compare the activities of proteases and their inhibitors in the hemolymph of workers reared in a small-cell comb (SMC) and a standard-cell comb (STC) in colonies kept simultaneously on standard- and small-cell combs. The width of comb cells in which workers are reared has a significant effect on the protein concentration and the proteolytic system in the hemolymph, which is reflected in the activities of proteases and their inhibitors. The protein concentrations in the 1-day-old workers were always higher (p ≤ 0.05) in the SMC than STC workers. The opposite was found in the older bee workers (aged 7, 14 and 21 d). The activities of proteases and their inhibitors in the 1-day-old workers were always higher (usually significantly at p ≤ 0.05) in STC than SMC workers, and opposite results were observed in the groups of the older workers (aged 7, 14 and 21 d). The differences between the workers from small-cell combs and those reared in standard-cell combs may be related to their different tasks. Workers reared in small-cell combs probably work as foragers outside the nest, whereas bees reared in standard-cell combs work in the nest. This hypothesis requires confirmation. To reduce the impact of accidental determinants on the results of single-season research on honeybees, it is advisable that such investigations should be conducted for several consecutive years.

Social immunity in honey bees: royal jelly as a vehicle in transferring bacterial pathogen fragments between nestmates

Social immunity is a suite of behavioral and physiological traits that allow colony members to protect one another from pathogens, and includes the oral transfer of immunological compounds between nestmates. In honey bees, royal jelly is a glandular secretion produced by a subset of workers that is fed to the queen and young larvae, and which contains many antimicrobial compounds. A related form of social immunity, transgenerational immune priming (TGIP), allows queens to transfer pathogen fragments into their developing eggs, where they are recognized by the embryo's immune system and induce higher pathogen resistance in the new offspring. These pathogen fragments are transported by vitellogenin (Vg), an egg-yolk precursor protein that is also used by nurses to synthesize royal jelly. Therefore, royal jelly may serve as a vehicle to transport pathogen fragments from workers to other nestmates. To investigate this, we recently showed that ingested bacteria are transported to nurses' jelly-producing glands, and here, we show that pathogen fragments are incorporated into the royal jelly. Moreover, we show that consuming pathogen cells induces higher levels of an antimicrobial peptide found in royal jelly, defensin-1.

Caveolin-1 Y14 phosphorylation suppresses tumor growth while promoting invasion

Caveolin-1 is a transmembrane protein with both tumor promoter and suppressor functions that remain poorly understood. Cav1 phosphorylation by Src kinase on tyrosine 14 is closely associated with focal adhesion dynamics and tumor cell migration, however the role of pCav1 in vivo in tumor progression remains poorly characterized. Herein, we expressed phosphomimetic Y14D, wild type, and non-phosphorylatable Y14F forms of Cav1 in MDA-MB-435 cancer cells. Expression of Cav1Y14D reduced cell proliferation and induced the TP53 tumor suppressor. Ectopic expression in MDA-MB-435 cells of Y14 phosphorylatable Cav1 was required for induction of TP53 in response to oxidative stress. Cav1Y14D promotes an apparent reversal of the Warburg effect and markedly inhibited tumor growth in vivo. However, Cav1 induced pseudopodial recruitment of glycolytic enzymes, and time-lapse intravital imaging showed increased invadopodia protrusion and extravasation into blood vessels for Cav1WT and Y14D but not for Y14F. Our results suggest that Cav1 Y14 phosphorylation levels play a role in the conflicting demands on metabolic resources associated with cancer cell proliferation versus motility.

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.

Expression of heat shock proteins in adult honey bee (Apis mellifera L.) workers under hot-arid subtropical ecosystems

Heat stress elicits the expression of heat shock proteins (HSPs) in honey bee subspecies. These highly conserved proteins have significant role in protecting cells from thermal-induced stresses. Honey bees in subtropical regions face extremely dry and hot environment. The expression of HSPs in the nurses and foragers of indigenous (Apis mellifera jemenitica) and imported European (Apis mellifera ligustica and Apis mellifera carnica) honey bee subspecies after heat shock treatment were compared using SDS-PAGE. Hsp70 and Hsp82 were equally expressed in the nurses of all tested bee subspecies when exposed to 40 °C and 45 °C for 4 h. The forager bees exhibited differential expression of HSPs after heat stress. No HSPs was expressed in the foragers of A. m. jemenitica, and Hsp70 was expressed only in the foragers of A. m. ligustica and A. m. carnica at 40 °C. A prominent diversity in HSPs expression was also exhibited in the foragers at 45 °C with one HSP (Hsp70) in A. m. jemenitica, two HSPs (Hsp40 and Hsp70) in A. m. carnica, and three HSPs (Hsp40, Hsp60 and Hsp70) in A. m. ligustica. No HSPs was expressed in the control nurse and forager bees at any of the tested temperatures. These findings illustrated the differences in HSP expression among nurse and forager bees. It is obvious that the native foragers are more heat tolerant with least HSPs expression than exotic bee races. Further investigations will help to understand the potential role of HSPs in the adaptability, survival, and performance of bee subspecies in harsh climate of the subtropical regions.

The Wisdom of Honeybee Defenses Against Environmental Stresses

As one of the predominant pollinator, honeybees provide important ecosystem service to crops and wild plants, and generate great economic benefit for humans. Unfortunately, there is clear evidence of recent catastrophic honeybee colony failure in some areas, resulting in markedly negative environmental and economic effects. It has been demonstrated that various environmental stresses, including both abiotic and biotic stresses, functioning singly or synergistically, are the potential drivers of colony collapse. Honeybees can use many defense mechanisms to decrease the damage from environmental stress to some extent. Here, we synthesize and summarize recent advances regarding the effects of environmental stress on honeybees and the wisdom of honeybees to respond to external environmental stress. Furthermore, we provide possible future research directions about the response of honeybees to various form of stressors.

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.

RNA-sequence analysis of gene expression from honeybees (Apis mellifera) infected with Nosema ceranae

Honeybees (Apis mellifera) are constantly subjected to many biotic stressors including parasites. This study examined honeybees infected with Nosema ceranae (N. ceranae). N. ceranae infection increases the bees energy requirements and may contribute to their decreased survival. RNA-seq was used to investigate gene expression at days 5, 10 and 15 Post Infection (P.I) with N. ceranae. The expression levels of genes, isoforms, alternative transcription start sites (TSS) and differential promoter usage revealed a complex pattern of transcriptional and post-transcriptional gene regulation suggesting that bees use a range of tactics to cope with the stress of N. ceranae infection. N. ceranae infection may cause reduced immune function in the bees by: (i)disturbing the host amino acids metabolism (ii) down-regulating expression of antimicrobial peptides (iii) down-regulation of cuticle coatings and (iv) down-regulation of odorant binding proteins.

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.

In-Depth N-Glycosylation Reveals Species-Specific Modifications and Functions of the Royal Jelly Protein from Western (Apis mellifera) and Eastern Honeybees (Apis cerana)

Royal jelly (RJ), secreted by honeybee workers, plays diverse roles as nutrients and defense agents for honeybee biology and human health. Despite being reported to be glycoproteins, the glycosylation characterization and functionality of RJ proteins in different honeybee species are largely unknown. An in-depth N-glycoproteome analysis and functional assay of RJ produced by Apis mellifera lingustica (Aml) and Apis cerana cerana (Acc) were conducted. RJ produced by Aml yielded 80 nonredundant N-glycoproteins carrying 190 glycosites, of which 23 novel proteins harboring 35 glycosites were identified. For Acc, all 43 proteins glycosylated at 138 glycosites were reported for the first time. Proteins with distinct N-glycoproteomic characteristics in terms of glycoprotein species, number of N-glycosylated sites, glycosylation motif, abundance level of glycoproteins, and N-glycosites were observed in this two RJ samples. The fact that the low inhibitory efficiency of N-glycosylated major royal jelly protein 2 (MRJP2) against Paenibacillus larvae (P. larvae) and the absence of antibacterial related glycosylated apidaecin, hymenoptaecin, and peritrophic matrix in the Aml RJ compared to Acc reveal the mechanism for why the Aml larvae are susceptible to P. larvae, the causative agent of a fatal brood disease (American foulbrood, AFB). The observed antihypertension activity of N-glycosylated MRJP1 in two RJ samples and a stronger activity found in Acc than in Aml reveal that specific RJ protein and modification are potentially useful for the treatment of hypertensive disease for humans. Our data gain novel understanding that the western and eastern bees have evolved species-specific strategies of glycosylation to fine-tune protein activity for optimizing molecular function as nutrients and immune agents for the good of honeybee and influence on the health promoting activity for human as well. This serves as a valuable resource for the targeted probing of the biological functions of RJ proteins for honeybee and medical communities.

A search for protein biomarkers links olfactory signal transduction to social immunity

Background

The Western honey bee (Apis mellifera L.) is a critical component of human agriculture through its pollination activities. For years, beekeepers have controlled deadly pathogens such as Paenibacillus larvae, Nosema spp. and Varroa destructor with antibiotics and pesticides but widespread chemical resistance is appearing and most beekeepers would prefer to eliminate or reduce the use of in-hive chemicals. While such treatments are likely to still be needed, an alternate management strategy is to identify and select bees with heritable traits that allow them to resist mites and diseases. Breeding such bees is difficult as the tests involved to identify disease-resistance are complicated, time-consuming, expensive and can misidentify desirable genotypes. Additionally, we do not yet fully understand the mechanisms behind social immunity. Here we have set out to discover the molecular mechanism behind hygienic behavior (HB), a trait known to confer disease resistance in bees.

Results

After confirming that HB could be selectively bred for, we correlated measurements of this behavior with protein expression over a period of three years, at two geographically distinct sites, using several hundred bee colonies. By correlating the expression patterns of individual proteins with HB scores, we identified seven putative biomarkers of HB that survived stringent control for multiple hypothesis testing. Intriguingly, these proteins were all involved in semiochemical sensing (odorant binding proteins), nerve signal transmission or signal decay, indicative of the series of events required to respond to an olfactory signal from dead or diseased larvae. We then used recombinant versions of two odorant-binding proteins to identify the classes of ligands that these proteins might be helping bees detect.

Conclusions

Our data suggest that neurosensory detection of odors emitted by dead or diseased larvae is the likely mechanism behind a complex and important social immunity behavior that allows bees to co-exist with pathogens.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-014-1193-6) contains supplementary material, which is available to authorized users.

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

BACKGROUND

Most of the proteins contained in royal jelly (RJ) are secreted from the hypopharyngeal glands (HG) of young bees. Although generic protein composition of RJ has been investigated, little is known about how age-dependent changes on HG secretion affect RJ composition and their biological consequences. In this study, we identified differentially expressed proteins (DEPs) during HG development by using the isobaric tag for relative and absolute quantification (iTRAQ) labeling technique. This proteomic method increases the potential for new protein discovery by improving the identification of low quantity proteins.

RESULTS

A total of 1282 proteins were identified from five age groups of worker bees, 284 of which were differentially expressed. 43 (15.1%) of the DEPs were identified for the first time. Comparison of samples at day 6, 9, 12, and 16 of development relative to day 3 led to the unambiguous identification of 112, 117, 127, and 127 DEPs, respectively. The majority of these DEPs were up-regulated in the older worker groups, indicating a substantial change in the pattern of proteins expressed after 3 days. DEPs were identified among all the age groups, suggesting that changes in protein expression during HG ontogeny are concomitant with different states of worker development. A total of 649 proteins were mapped to canonical signaling pathways found in the Kyoto Encyclopedia of Genes and Genomes (KEGG), which were preferentially associated with metabolism and biosynthesis of secondary metabolites. More than 10 key high-abundance proteins were involved in signaling pathways related to ribosome function and protein processing in the endoplasmic reticulum. The results were validated by qPCR.

CONCLUSION

Our approach demonstrates that HG experienced important changes in protein expression during its ontogenic development, which supports the secretion of proteins involved in diverse functions in adult workers beyond its traditional role in royal jelly production.

Hemolymph proteome changes during worker brood development match the biological divergences between western honey bees (Apis mellifera) and eastern honey bees (Apis cerana)

Background

Hemolymph plays key roles in honey bee molecule transport, immune defense, and in monitoring the physiological condition. There is a lack of knowledge regarding how the proteome achieves these biological missions for both the western and eastern honey bees (Apis mellifera and Apis cerana). A time-resolved proteome was compared using two-dimensional electrophoresis-based proteomics to reveal the mechanistic differences by analysis of hemolymph proteome changes between the worker bees of two bee species during the larval to pupal stages.

Results

The brood body weight of Apis mellifera was significantly heavier than that of Apis cerana at each developmental stage. Significantly, different protein expression patterns and metabolic pathways were observed in 74 proteins (166 spots) that were differentially abundant between the two bee species. The function of hemolymph in energy storage, odor communication, and antioxidation is of equal importance for the western and eastern bees, indicated by the enhanced expression of different protein species. However, stronger expression of protein folding, cytoskeletal and developmental proteins, and more highly activated energy producing pathways in western bees suggests that the different bee species have developed unique strategies to match their specific physiology using hemolymph to deliver nutrients and in immune defense.

Conclusions

Our disparate findings constitute a proof-of-concept of molecular details that the ecologically shaped different physiological conditions of different bee species match with the hemolymph proteome during the brood stage. This also provides a starting point for future research on the specific hemolymph proteins or pathways related to the differential phenotypes or physiology.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2164-15-563) contains supplementary material, which is available to authorized users.

Effect of bodily fluids from honey bee (Apis mellifera) larvae on growth and genome-wide transcriptional response of the causal agent of American Foulbrood disease (Paenibacillus larvae)

Paenibacillus larvae, the causal agent of American Foulbrood disease (AFB), affects honey bee health worldwide. The present study investigates the effect of bodily fluids from honey bee larvae on growth velocity and transcription for this Gram-positive, endospore-forming bacterium. It was observed that larval fluids accelerate the growth and lead to higher bacterial densities during stationary phase. The genome-wide transcriptional response of in vitro cultures of P. larvae to larval fluids was studied by microarray technology. Early responses of P. larvae to larval fluids are characterized by a general down-regulation of oligopeptide and sugar transporter genes, as well as by amino acid and carbohydrate metabolic genes, among others. Late responses are dominated by general down-regulation of sporulation genes and up-regulation of phage-related genes. A theoretical mechanism of carbon catabolite repression is discussed.

Finding the missing honey bee genes: lessons learned from a genome upgrade

Background

The first generation of genome sequence assemblies and annotations have had a significant impact upon our understanding of the biology of the sequenced species, the phylogenetic relationships among species, the study of populations within and across species, and have informed the biology of humans. As only a few Metazoan genomes are approaching finished quality (human, mouse, fly and worm), there is room for improvement of most genome assemblies. The honey bee (Apis mellifera) genome, published in 2006, was noted for its bimodal GC content distribution that affected the quality of the assembly in some regions and for fewer genes in the initial gene set (OGSv1.0) compared to what would be expected based on other sequenced insect genomes.

Results

Here, we report an improved honey bee genome assembly (Amel_4.5) with a new gene annotation set (OGSv3.2), and show that the honey bee genome contains a number of genes similar to that of other insect genomes, contrary to what was suggested in OGSv1.0. The new genome assembly is more contiguous and complete and the new gene set includes ~5000 more protein-coding genes, 50% more than previously reported. About 1/6 of the additional genes were due to improvements to the assembly, and the remaining were inferred based on new RNAseq and protein data.

Conclusions

Lessons learned from this genome upgrade have important implications for future genome sequencing projects. Furthermore, the improvements significantly enhance genomic resources for the honey bee, a key model for social behavior and essential to global ecology through pollination.

Honey bee protein atlas at organ-level resolution

Genome sequencing has provided us with gene lists but cannot tell us where and how their encoded products work together to support life. Complex organisms rely on differential expression of subsets of genes/proteins in organs and tissues, and, in concert, evolved to their present state as they function together to improve an organism's overall reproductive fitness. Proteomics studies of individual organs help us understand their basic functions, but this reductionist approach misses the larger context of the whole organism. This problem could be circumvented if all the organs in an organism were comprehensively studied by the same methodology and analyzed together. Using honey bees (Apis mellifera L.) as a model system, we report here an initial whole proteome of a complex organism, measuring 29 different organ/tissue types among the three honey bee castes: queen, drone, and worker. The data reveal that, e.g., workers have a heightened capacity to deal with environmental toxins and queens have a far more robust pheromone detection system than their nestmates. The data also suggest that workers altruistically sacrifice not only their own reproductive capacity but also their immune potential in favor of their queen. Finally, organ-level resolution of protein expression offers a systematic insight into how organs may have developed.

Proteomic analysis identifies a novel function for galectin-3 in the cell entry of parvovirus

Cellular factors associated with the parvovirus minute virus of mice (MVM) during infection are thought to play important roles in the MVM life cycle but only a few of these have been identified. Here we used a proteomic-based approach in order to identify host-binding partners of MVM. Using purified MVM as bait for immunoprecipitation assays, a total of 150 proteins were identified in MVM immunoprecipitates by quantitative liquid chromatography-tandem mass spectrometry. Galectin-3 was one of six proteins showing a statistically significant enrichment across replicates. Small interfering RNA depletion studies revealed an important role for galectin-3 in MVM endocytosis and infectivity in LA9 mouse fibroblast cells. Galectin-3-depleted cells were less susceptible to MVM infection than control cells and showed a significant reduction of MVM cellular uptake, but not of MVM binding to the cell surface. Our results indicate an important role for galectin-3 in the cellular uptake of MVM. We propose that galectin-3 facilitates the access of MVM to its receptor(s) at the plasma membrane and in this way promotes MVM endocytosis.

Honey bee drones maintain humoral immune competence throughout all life stages in the absence of vitellogenin production

Drones are haploid male individuals whose major social function in honey bee colonies is to produce sperm and mate with a queen. In spite of their limited tasks, the vitality of drones is of utmost importance for the next generation. The immune competence of drones - as compared to worker bees - is largely unexplored. Hence, we studied humoral and cellular immune reactions of in vitro reared drone larvae and adult drones of different age upon artificial bacterial infection. Haemolymph samples were collected after aseptic and septic injury and subsequently employed for (1) the identification of immune-responsive peptides and/or proteins by qualitative proteomic analyses in combination with mass spectrometry and (2) the detection of antimicrobial activity by inhibition-zone assays. Drone larvae and adult drones responded with a strong humoral immune reaction upon bacterial challenge, as validated by the expression of small antimicrobial peptides. Young adult drones exhibited a broader spectrum of defence reactions than drone larvae. Distinct polypeptides including peptidoglycan recognition protein-S2 and lysozyme 2 were upregulated in immunized adult drones. Moreover, a pronounced nodulation reaction was observed in young drones upon bacterial challenge. Prophenoloxidase zymogen is present at an almost constant level in non-infected adult drones throughout the entire lifespan. All observed immune reactions in drones were expressed in the absence of significant amounts of vitellogenin. We conclude that drones - like worker bees - have the potential to activate multiple elements of the innate immune response.

Differential impact of caveolae and caveolin-1 scaffolds on the membrane raft proteome

Caveolae, a class of cholesterol-rich lipid rafts, are smooth invaginations of the plasma membrane whose formation in nonmuscle cells requires caveolin-1 (Cav1). The recent demonstration that Cav1-associated cavin proteins, in particular PTRF/cavin-1, are also required for caveolae formation supports a functional role for Cav1 independently of caveolae. In tumor cells deficient for Golgi β-1,6N-acetylglucosaminyltransferase V (Mgat5), reduced Cav1 expression is associated not with caveolae but with oligomerized Cav1 domains, or scaffolds, that functionally regulate receptor signaling and raft-dependent endocytosis. Using subdiffraction-limit microscopy, we show that Cav1 scaffolds are homogenous subdiffraction-limit sized structures whose size distribution differs from that of Cav1 in caveolae expressing cells. These cell lines displaying differing Cav1/caveolae phenotypes are effective tools for probing the structure and composition of caveolae. Using stable isotope labeling by amino acids in cell culture, we are able to quantitatively distinguish the composition of caveolae from the background of detergent-resistant membrane proteins and show that the presence of caveolae enriches the protein composition of detergent-resistant membrane, including the recruitment of multiple heterotrimeric G-protein subunits. These data were further supported by analysis of immuno-isolated Cav1 domains and of methyl-β-cyclodextrin-disrupted detergent-resistant membrane. Our data show that loss of caveolae results in a dramatic change to the membrane raft proteome and that this change is independent of Cav1 expression. The proteomics data, in combination with subdiffraction-limit microscopy, indicates that noncaveolar Cav1 domains, or scaffolds are structurally and functionally distinct from caveolae and differentially impact on the molecular composition of lipid rafts.

Differential proteomics in dequeened honeybee colonies reveals lower viral load in hemolymph of fertile worker bees

The eusocial societies of honeybees, where the queen is the only fertile female among tens of thousands sterile worker bees, have intrigued scientists for centuries. The proximate factors, which cause the inhibition of worker bee ovaries, remain largely unknown; as are the factors which cause the activation of worker ovaries upon the loss of queen and brood in the colony. In an attempt to reveal key players in the regulatory network, we made a proteomic comparison of hemolymph profiles of workers with completely activated ovaries vs. rudimentary ovaries. An unexpected finding of this study is the correlation between age matched worker sterility and the enrichment of Picorna-like virus proteins. Fertile workers, on the other hand, show the upregulation of potential components of the immune system. It remains to be investigated whether viral infections contribute to worker sterility directly or are the result of a weaker immune system of sterile workers.

A honey bee (Apis mellifera L.) PeptideAtlas crossing castes and tissues

BACKGROUND

Honey bees are a mainstay of agriculture, contributing billions of dollars through their pollination activities. Bees have been a model system for sociality and group behavior for decades but only recently have molecular techniques been brought to study this fascinating and valuable organism. With the release of the first draft of its genome in 2006, proteomics of bees became feasible and over the past five years we have amassed in excess of 5E+6 MS/MS spectra. The lack of a consolidated platform to organize this massive resource hampers our ability, and that of others, to mine the information to its maximum potential.

RESULTS

Here we introduce the Honey Bee PeptideAtlas, a web-based resource for visualizing mass spectrometry data across experiments, providing protein descriptions and Gene Ontology annotations where possible. We anticipate that this will be helpful in planning proteomics experiments, especially in the selection of transitions for selected reaction monitoring. Through a proteogenomics effort, we have used MS/MS data to anchor the annotation of previously undescribed genes and to re-annotate previous gene models in order to improve the current genome annotation.

CONCLUSIONS

The Honey Bee PeptideAtlas will contribute to the efficiency of bee proteomics and accelerate our understanding of this species. This publicly accessible and interactive database is an important framework for the current and future analysis of mass spectrometry data.

Proteomic analysis of honeybee (Apis mellifera L.) pupae head development

The honeybee pupae development influences its future adult condition as well as honey and royal jelly productions. However, the molecular mechanism that regulates honeybee pupae head metamorphosis is still poorly understood. To further our understand of the associated molecular mechanism, we investigated the protein change of the honeybee pupae head at 5 time-points using 2-D electrophoresis, mass spectrometry, bioinformatics, quantitative real-time polymerase chain reaction and Western blot analysis. Accordingly, 58 protein spots altered their expression across the 5 time points (13–20 days), of which 36 proteins involved in the head organogenesis were upregulated during early stages (13–17 days). However, 22 proteins involved in regulating the pupae head neuron and gland development were upregulated at later developmental stages (19–20 days). Also, the functional enrichment analysis further suggests that proteins related to carbohydrate metabolism and energy production, development, cytoskeleton and protein folding were highly involved in the generation of organs and development of honeybee pupal head. Furthermore, the constructed protein interaction network predicted 33 proteins acting as key nodes of honeybee pupae head growth of which 9 and 4 proteins were validated at gene and protein levels, respectively. In this study, we uncovered potential protein species involved in the formation of honeybee pupae head development along with their specific temporal requirements. This first proteomic result allows deeper understanding of the proteome profile changes during honeybee pupae head development and provides important potential candidate proteins for future reverse genetic research on honeybee pupae head development to improve the performance of related organs.

Biomarkers for severity of spinal cord injury in the cerebrospinal fluid of rats

One of the major challenges in management of spinal cord injury (SCI) is that the assessment of injury severity is often imprecise. Identification of reliable, easily quantifiable biomarkers that delineate the severity of the initial injury and that have prognostic value for the degree of functional recovery would significantly aid the clinician in the choice of potential treatments. To find such biomarkers we performed quantitative liquid chromatography-mass spectrometry (LC-MS/MS) analyses of cerebrospinal fluid (CSF) collected from rats 24 h after either a moderate or severe SCI. We identified a panel of 42 putative biomarkers of SCI, 10 of which represent potential biomarkers of SCI severity. Three of the candidate biomarkers, Ywhaz, Itih4, and Gpx3 were also validated by Western blot in a biological replicate of the injury. The putative biomarkers identified in this study may potentially be a valuable tool in the assessment of the extent of spinal cord damage.

Honeybee (Apis mellifera ligustica) drone embryo proteomes

Little attention has been paid to the drone honeybee (Apis mellifera ligustica) which is a haploid individual carrying only the set of alleles that it inherits from its mother. Molecular mechanisms underlying drone embryogenesis are poorly understood. This study evaluated protein expression profiles of drone embryogenesis at embryonic ages of 24, 48 and 72h. More than 100 reproducible proteins were analyzed by mass spectrometry on 2D electrophoresis gels. Sixty-two proteins were significantly changed at the selected three experimental age points. Expression of the metabolic energy requirement-related protein peaked at the embryonic age of 48h, whereas development and metabolizing amino acid-related proteins expressed optimally at 72h. Cytoskeleton, protein folding and antioxidant-related proteins were highly expressed at 48 and 72h. Protein networks of the identified proteins were constructed and protein expressions were validated at the transcription level. This first proteomic study of drone embryogenesis in the honeybee may provide geneticists an exact timetable and candidate protein outline for further manipulations of drone stem cells.

Proteomic characterization of aggregating proteins after the inhibition of the ubiquitin proteasome system

Protein aggregation, which is associated with the impairment of the ubiquitin proteasome system, is a hallmark of many neurodegenerative diseases. To better understand the contribution of proteasome inhibition in aggregation, we analyzed which proteins may potentially localize in chemically induced aggregates in human neuroblastoma tissue culture cells. We enriched for proteins in high-density structures by using a sucrose gradient in combination with stable isotope labeling with amino acids in cell culture (SILAC). The quantitative analysis allowed us to distinguish which proteins were specifically affected by the proteasome inhibition. We identified 642 potentially aggregating proteins, including the p62/sequestosome 1 and NBR1 ubiquitin-binding proteins involved in aggregation. We also identified the ubiquitin-associated protein 2 like (UBAP2L). We verified that it cofractionated with ubiquitin in the high-density fraction and that it was colocalized in the ubiquitin-containing aggregates after proteasome inhibition. In addition, we identified several chaperone proteins and used data from protein interaction networks to show that they potentially interact with distinct subgroups of proteins within the aggregating structures. Several other proteins associated with neurodegenerative diseases, like UCHL1, were identified, further underlining the potential of our analysis to better understand the aggregation process and proteotoxic stress caused by proteasome inhibition.

Mapping the protein interaction network in methicillin-resistant Staphylococcus aureus

Mortality attributable to infection with methicillin-resistant Staphylococcus aureus (MRSA) has now overtaken the death rate for AIDS in the United States, and advances in research are urgently needed to address this challenge. We report the results of the systematic identification of protein-protein interactions for the hospital-acquired strain MRSA-252. Using a high-throughput pull-down strategy combined with quantitative proteomics to distinguish specific from nonspecific interactors, we identified 13,219 interactions involving 608 MRSA proteins. Consecutive analyses revealed that this protein interaction network (PIN) exhibits scale-free organization with the characteristic presence of highly connected hub proteins. When clinical and experimental antimicrobial targets were queried in the network, they were generally found to occupy peripheral positions in the PIN with relatively few interacting partners. In contrast, the hub proteins identified in this MRSA PIN that are essential for network integrity and stability have largely been overlooked as drug targets. Thus, this empirical MRSA-252 PIN provides a rich source for identifying critical proteins essential for network stability, many of which can be considered as prospective antimicrobial drug targets.

Differential protein expression in honeybee (Apis mellifera L.) larvae: underlying caste differentiation

Honeybee (Apis mellifera) exhibits divisions in both morphology and reproduction. The queen is larger in size and fully developed sexually, while the worker bees are smaller in size and nearly infertile. To better understand the specific time and underlying molecular mechanisms of caste differentiation, the proteomic profiles of larvae intended to grow into queen and worker castes were compared at 72 and 120 hours using two dimensional electrophoresis (2-DE), network, enrichment and quantitative PCR analysis. There were significant differences in protein expression between the two larvae castes at 72 and 120 hours, suggesting the queen and the worker larvae have already decided their fate before 72 hours. Specifically, at 72 hours, queen intended larvae over-expressed transketolase, aldehyde reductase, and enolase proteins which are involved in carbohydrate metabolism and energy production, imaginal disc growth factor 4 which is a developmental related protein, long-chain-fatty-acid CoA ligase and proteasome subunit alpha type 5 which metabolize fatty and amino acids, while worker intended larvae over-expressed ATP synthase beta subunit, aldehyde dehydrogenase, thioredoxin peroxidase 1 and peroxiredoxin 2540, lethal (2) 37 and 14-3-3 protein epsilon, fatty acid binding protein, and translational controlled tumor protein. This differential protein expression between the two caste intended larvae was more pronounced at 120 hours, with particular significant differences in proteins associated with carbohydrate metabolism and energy production. Functional enrichment analysis suggests that carbohydrate metabolism and energy production and anti-oxidation proteins play major roles in the formation of caste divergence. The constructed network and validated gene expression identified target proteins for further functional study. This new finding is in contrast to the existing notion that 72 hour old larvae has bipotential and can develop into either queen or worker based on epigenetics and can help us to gain new insight into the time of departure as well as caste trajectory influencing elements at the molecular level.

Ecological adaptation of diverse honey bee (Apis mellifera) populations

Background

Honey bees are complex eusocial insects that provide a critical contribution to human agricultural food production. Their natural migration has selected for traits that increase fitness within geographical areas, but in parallel their domestication has selected for traits that enhance productivity and survival under local conditions. Elucidating the biochemical mechanisms of these local adaptive processes is a key goal of evolutionary biology. Proteomics provides tools unique among the major ‘omics disciplines for identifying the mechanisms employed by an organism in adapting to environmental challenges.

Results

Through proteome profiling of adult honey bee midgut from geographically dispersed, domesticated populations combined with multiple parallel statistical treatments, the data presented here suggest some of the major cellular processes involved in adapting to different climates. These findings provide insight into the molecular underpinnings that may confer an advantage to honey bee populations. Significantly, the major energy-producing pathways of the mitochondria, the organelle most closely involved in heat production, were consistently higher in bees that had adapted to colder climates. In opposition, up-regulation of protein metabolism capacity, from biosynthesis to degradation, had been selected for in bees from warmer climates.

Conclusions

Overall, our results present a proteomic interpretation of expression polymorphisms between honey bee ecotypes and provide insight into molecular aspects of local adaptation or selection with consequences for honey bee management and breeding. The implications of our findings extend beyond apiculture as they underscore the need to consider the interdependence of animal populations and their agro-ecological context.

PSORTb 3.0: improved protein subcellular localization prediction with refined localization subcategories and predictive capabilities for all prokaryotes

Motivation: PSORTb has remained the most precise bacterial protein subcellular localization (SCL) predictor since it was first made available in 2003. However, the recall needs to be improved and no accurate SCL predictors yet make predictions for archaea, nor differentiate important localization subcategories, such as proteins targeted to a host cell or bacterial hyperstructures/organelles. Such improvements should preferably be encompassed in a freely available web-based predictor that can also be used as a standalone program.

Results: We developed PSORTb version 3.0 with improved recall, higher proteome-scale prediction coverage, and new refined localization subcategories. It is the first SCL predictor specifically geared for all prokaryotes, including archaea and bacteria with atypical membrane/cell wall topologies. It features an improved standalone program, with a new batch results delivery system complementing its web interface. We evaluated the most accurate SCL predictors using 5-fold cross validation plus we performed an independent proteomics analysis, showing that PSORTb 3.0 is the most accurate but can benefit from being complemented by Proteome Analyst predictions.

Availability:http://www.psort.org/psortb (download open source software or use the web interface).

Contact:psort-mail@sfu.ca

Supplementary Information:Supplementary data are availableat Bioinformatics online.

Pseudopodial actin dynamics control epithelial-mesenchymal transition in metastatic cancer cells

A key cellular process associated with the invasive or metastatic program in many cancers is the transformation of epithelial cells toward a mesenchymal state, a process called epithelial to mesenchymal transition or EMT. Actin-dependent protrusion of cell pseudopodia is a critical element of mesenchymal cell migration and therefore of cancer metastasis. However, whether EMT occurs in human cancers and, in particular, whether it is a prerequisite for tumor cell invasion and metastasis, remains a subject of debate. Microarray and proteomic analysis of actin-rich pseudopodia from six metastatic human tumor cell lines identified 384 mRNAs and 64 proteins common to the pseudopodia of six metastatic human tumor cell lines of various cancer origins leading to the characterization of 19 common pseudopod-specific proteins. Four of these (AHNAK, septin-9, eIF4E, and S100A11) are shown to be essential for pseudopod protrusion and tumor cell migration and invasion. Knockdown of each of these proteins in metastatic cells resulted in reduced actin cytoskeleton dynamics and induction of mesenchymal-epithelial transition (MET) that could be prevented by the stabilization of the actin cytoskeleton. Actin-dependent pseudopodial protrusion and tumor cell migration are therefore determinants of EMT. Protein regulators of pseudopodial actin dynamics may represent unique molecular targets to induce MET and thereby inhibit the metastatic potential of tumor cells.

MSQuant, an open source platform for mass spectrometry-based quantitative proteomics

Mass spectrometry-based proteomics critically depends on algorithms for data interpretation. A current bottleneck in the rapid advance of proteomics technology is the closed nature and slow development cycle of vendor-supplied software solutions. We have created an open source software environment, called MSQuant, which allows visualization and validation of peptide identification results directly on the raw mass spectrometric data. MSQuant iteratively recalibrates MS data thereby significantly increasing mass accuracy leading to fewer false positive peptide identifications. Algorithms to increase data quality include an MS(3) score for peptide identification and a post-translational modification (PTM) score that determines the probability that a modification such as phosphorylation is placed at a specific residue in an identified peptide. MSQuant supports relative protein quantitation based on precursor ion intensities, including element labels (e.g., (15)N), residue labels (e.g., SILAC and ICAT), termini labels (e.g., (18)O), functional group labels (e.g., mTRAQ), and label-free ion intensity approaches. MSQuant is available, including an installer and supporting scripts, at http://msquant.sourceforge.net .

An exosome-based secretion pathway is responsible for protein export from Leishmania and communication with macrophages

Specialized secretion systems are used by numerous bacterial pathogens to export virulence factors into host target cells. Leishmania and other eukaryotic intracellular pathogens also deliver effector proteins into host cells; however, the mechanisms involved have remained elusive. In this report, we identify exosome-based secretion as a general mechanism for protein secretion by Leishmania, and show that exosomes are involved in the delivery of proteins into host target cells. Comparative quantitative proteomics unambiguously identified 329 proteins in Leishmania exosomes, accounting for >52% of global protein secretion from these organisms. Our findings demonstrate that infection-like stressors (37 degrees C +/- pH 5.5) upregulated exosome release more than twofold and also modified exosome protein composition. Leishmania exosomes and exosomal proteins were detected in the cytosolic compartment of infected macrophages and incubation of macrophages with exosomes selectively induced secretion of IL-8, but not TNF-alpha. We thus provide evidence for an apparently broad-based mechanism of protein export by Leishmania. Moreover, we describe a mechanism for the direct delivery of Leishmania molecules into macrophages. These findings suggest that, like mammalian exosomes, Leishmania exosomes function in long-range communication and immune modulation.

The innate immune and systemic response in honey bees to a bacterial pathogen, Paenibacillus larvae

Background

There is a major paradox in our understanding of honey bee immunity: the high population density in a bee colony implies a high rate of disease transmission among individuals, yet bees are predicted to express only two-thirds as many immunity genes as solitary insects, e.g., mosquito or fruit fly. This suggests that the immune response in bees is subdued in favor of social immunity, yet some specific immune factors are up-regulated in response to infection. To explore the response to infection more broadly, we employ mass spectrometry-based proteomics in a quantitative analysis of honey bee larvae infected with the bacterium Paenibacillus larvae. Newly-eclosed bee larvae, in the second stage of their life cycle, are susceptible to this infection, but become progressively more resistant with age. We used this host-pathogen system to probe not only the role of the immune system in responding to a highly evolved infection, but also what other mechanisms might be employed in response to infection.

Results

Using quantitative proteomics, we compared the hemolymph (insect blood) of five-day old healthy and infected honey bee larvae and found a strong up-regulation of some metabolic enzymes and chaperones, while royal jelly (food) and energy storage proteins were down-regulated. We also observed increased levels of the immune factors prophenoloxidase (proPO), lysozyme and the antimicrobial peptide hymenoptaecin. Furthermore, mass spectrometry evidence suggests that healthy larvae have significant levels of catalytically inactive proPO in the hemolymph that is proteolytically activated upon infection. Phenoloxidase (PO) enzyme activity was undetectable in one or two-day-old larvae and increased dramatically thereafter, paralleling very closely the age-related ability of larvae to resist infection.

Conclusion

We propose a model for the host response to infection where energy stores and metabolic enzymes are regulated in concert with direct defensive measures, such as the massive enhancement of PO activity.