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

Extending the honey bee venome with the antimicrobial peptide apidaecin and a protein resembling wasp antigen 5

Honey bee venom is a complex mixture of toxic proteins and peptides. In the present study we tried to extend our knowledge of the venom composition using two different approaches. First, worker venom was analysed by liquid chromatography-mass spectrometry and this revealed the antimicrobial peptide apidaecin for the first time in such samples. Its expression in the venom gland was confirmed by reverse transcription PCR and by a peptidomic analysis of the venom apparatus tissue. Second, genome mining revealed a list of proteins with resemblance to known insect allergens or venom toxins, one of which showed homology to proteins of the antigen 5 (Ag5)/Sol i 3 cluster. It was demonstrated that the honey bee Ag5-like gene is expressed by venom gland tissue of winter bees but not of summer bees. Besides this seasonal variation, it shows an interesting spatial expression pattern with additional production in the hypopharyngeal glands, the brains and the midgut. Finally, our immunoblot study revealed that both synthetic apidaecin and the Ag5-like recombinant from bacteria evoke no humoral activity in beekeepers. Also, no IgG4-based cross-reactivity was detected between the honey bee Ag5-like protein and its yellow jacket paralogue Ves v 5

Genome-wide analysis of alternative reproductive phenotypes in honeybee workers

A defining feature of social insects is the reproductive division of labour, in which workers usually forego all reproduction to help their mother queen to reproduce. However, little is known about the molecular basis of this spectacular form of altruism. Here, we compared gene expression patterns between nonreproductive, altruistic workers and reproductive, non-altruistic workers in queenless honeybee colonies using a whole-genome microarray analysis. Our results demonstrate massive differences in gene expression patterns between these two sets of workers, with a total of 1292 genes being differentially expressed. In nonreproductive workers, genes associated with energy metabolism and respiration, flight and foraging behaviour, detection of visible light, flight and heart muscle contraction and synaptic transmission were overexpressed relative to reproductive workers. This implies they probably had a higher whole-body energy metabolism and activity rate and were most likely actively foraging, whereas same-aged reproductive workers were not. This pattern is predicted from evolutionary theory, given that reproductive workers should be less willing to compromise their reproductive futures by carrying out high-risk tasks such as foraging or other energetically expensive tasks. By contrast, reproductive workers mainly overexpressed oogenesis-related genes compared to nonreproductive ones. With respect to key switches for ovary activation, several genes involved in steroid biosynthesis were upregulated in reproductive workers, as well as genes known to respond to queen and brood pheromones, genes involved in TOR and insulin signalling pathways and genes located within quantitative trait loci associated with reproductive capacity in honeybees. Overall, our results provide unique insight into the molecular mechanisms underlying alternative reproductive phenotypes in honeybee workers

Allocation of worker policing in the honeybee Apis mellifera

The classic view of insect colonies as harmonic societies has been challenged in the last decades. It became clear that several conflicts ‘loom’ below the peaceful surface. One conflict is about male parentage, as some workers are capable of producing viable male eggs and are sometimes favoured by selection to do so. Yet, there are methods in place to reduce or solve these conflicts. Worker policing in social Hymenoptera (by removal of worker laid eggs) was predicted in 1984 and first reported in the honeybee (Apis mellifera) in 1989. Various models try to explain the origin and maintenance of policing in terms of inclusive fitness theory. Much effort has been invested into the search for signals or cues of egg provenance. Less is known about the organization of policing within a colony. Recent studies in several taxa suggest a specialization in policing behaviour. We aim to provide the first insight into the task allocation of worker policing in honeybees. Therefore, we will follow cohorts of individually marked bees of known age in an observation hive, using focal sampling methods, to study the work profile of policing honeybee workers. A predisposition for policing might be indicated by inspecting cells, especially on drone combs. By introducing worker laid eggs in drone cells, we will be able to observe actual events of policing. Policing and non-policing bees of the same age will be sampled and their ovaries dissected. A possibly inherited bias for policing will be detected by microsatellite analysis of patrilines. Starr C.K. 1984. in: Sperm competition and the evolution of animal mating systems. (ed. Smith R. L.) 427-464 2 Ratnieks F.L.W, Vischer P.K. 1989. Nature 342: 796-797 3 Ratnieks F.L.W. et al. 2006. Annu. Rev. Entomol. 51: 581-608 4 Martin S.J. et al. 2005. J. Negat. Res. Ecol. Evol. 2: 1-9 5 Van Zweden J.S. et al. 2007. Proc. R. Soc. B 274: 1421-1428status: publishe

Worker honeybee sterility: a proteomic analysis of suppressed ovary activation

Eusocial behavior is extensively studied in the honeybee, Apis mellifera, as it displays an extreme form of altruism. Honeybee workers are generally obligatory sterile in a bee colony headed by a queen, but the inhibition of ovary activation is lifted upon the absence of queen and larvae. Worker bees are then able to develop mature, viable eggs. The detailed repressive physiological mechanisms which are responsible for this remarkable phenomenon are as yet largely unknown. Physiological studies today mainly focus on the transcriptome, while the proteome stays rather unexplored. Here, we present a quantitative 2-dimensional differential gel electrophoresis comparison between activated and inactivated worker ovaries and brains of reproductive and sterile worker bees, including a spot map of ovaries, containing 197 identified spots. Our findings suggest that suppression of ovary activation might involve a constant interplay between primordial oogenesis and subsequent degradation, which is probably mediated through steroid and neuropeptide hormone signaling. Additionally, the observation of higher viral protein loads in both the brains and ovaries of sterile workers is particularly noteworthy. This dataset will be of great value for future research unraveling the physiological mechanisms underlying the altruistic sterility in honeybee workers.status: publishe