The effect of the brood and the queen on early gene expression in bumble bee workers' brains
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ABSTRACT: We used RNA-se to compare gene expression patterns in workers of the bumble bee Bombus impatiens in response to the queen, the brood, both or none.
Project description:Social organization is commonly dynamic with extreme examples in annual eusocial insects ("annual superorganisms"), but the signals and mechanisms regulating social organization remained elusive. In annual bumble bee colonies, larvae with a close contact to a queen do not differentiate into gynes, pupate at an earlier age, and are commonly smaller than siblings that do not contact a queen. We combined detailed observations, proteomics, microRNA transcriptomics, and gland removal surgery, to study the regulation of brood development and division of labor in the model bumble bee Bombus terrestris. We found that regurgitates fed to larvae by queens and workers differ in their protein and microRNA composition. The proteome of the regurgitate overlaps significantly with that of the mandibular (MG) and hypopharyngeal glands (HPG), suggesting that these exocrine glands are the sources of some regurgitate proteins. The MG and HPG proteomes , but not that of the salivary glands, differed between queens and workers, with the caste-specificity preserved for the MG and regurgitate proteomes. Queens subjected to a surgical removal of the MG showed normal behavior and brood care, but failed to manipulate the developmental program of the brood they reared. These findings suggest that substances in the queen MG are fed to larvae and influence their developmental program. As the colony grows, an increasing number of workers feed larvae and by that reduce the effects of the queen substances, such that she can no longer manipulate the development of all larvae, and the colony switches from producing workers (ergonomic phase) to gynes (reproductive phase).
Project description:During the nest-founding phase of the bumble bee colony cycle, queens undergo striking changes in maternal care behavior. Early in the founding phase, prior to the emergence of workers in the nest, queens are reproductive and also provision and feed their offspring. However, later in the founding phase, queens cease feeding offspring and become specialized on reproduction. This transition is synchronized with the emergence of workers in the colony, who assume the task of feeding their siblings. Using a social manipulation experiment, we tested the hypothesis that workers socially regulate the transition from feeding brood to specialization on reproduction in nest-founding bumble bee queens. Consistent with this hypothesis, we found that early-stage queens with workers prematurely added to their nests reduce their brood-feeding behavior and increase egg-laying, and likewise, late-stage queens increase their brood-feeding behavior and decrease egg-laying when workers are removed from their nests. Further, brood-feeding and egg-laying behavior were negatively correlated in these queens. We used an Agilent brain EST-based microarray to explore a second hypothesis, that workers alter brain gene expression in nest-founding queens. We found evidence that brain gene expression in nest-founding queens is altered by the presence of workers, with the effect much stronger in late-stage founding queens. Additionally, expression levels of some genes were correlated with quantitative differences in brood-feeding and egg-laying behavior. This study provides new insights into how the transition from feeding brood to specialization on reproduction in bumble bee queens is regulated during the nest initiation phase of the colony cycle.
Project description:Our aim was to identify the genes that are responsible for caste differentiation in the primitively eusocial bumble bee, Bombus terrestris. To do this we extracted RNA from both queen- and worker-destined larvae. We extracted RNA from three key stages during bumble bee development (before, during, and after their caste becomes fixed), and then sent the sequencing to the Earlham Institute. They used mRNAseq to isolate the RNA from each developmental stage and caste pathway.
Project description:We used whole-genome fire ant microarrays to examine the molecular basis for social organization in Solenopsis invicta. Monogyne (single queen) fire ant colonies were collected in the field and transported into the lab were they were reared in standard conditions for two weeks. At this point, each colony was split into two sub-colonies: one sub-colony contained the functional mother queen (queenright) while the other was left queenless. Each sub-colony included a nesting chamber, containing the brood and workers performing nursing tasks, and a foraging area, separated from the nesting chamber and provided with food and water sources. For both queenright and queenless sub-colonies, foraging workers were collected in the foraging area while non-foraging workers were collected in the nesting chamber. Total RNA was isolated from pools of 10 whole workers and processed for microarrays.
Project description:RNA-seq from whole bodies of workers (major and minor) and queen from C. floridanus to increase replicate number from 2010 genome study
Project description:Our aims in this study were: 1) to identify the miRNAs of the bumble bees Bombus terrestris and B. impatiens; 2) to compare the total numbers of miRNAs between both bumble bee species and between them and the honey bee, Apis mellifera; and 3) to test whether the sequences and expression patterns of miRNAs were conserved between species. To investigate each of these aims we used miRNA-seq (deep sequencing of miRNA-enriched libraries) in B. terrestris, and bioinformatics prediction programs to identify miRNAs in both Bombus species. We identified 131 miRNAs in B. terrestris, and 114 in B. impatiens; of these, 17 were new miRNAs that had not previously been sequenced in any species. We found a striking level of difference in the miRNAs present between Bombus and A. mellifera, with 103 miRNAs in A. mellifera not being present in the genomes of the two bumble bees. miRNA profiles of Bombus terrestris at two developmental stages in larvae. This submission represents 'Bombus terrestris' component of study.
Project description:Responses to social cues, such as pheromones, can be modified by genotype, physiology, or environmental context. Honey bee queens produce a pheromone (queen mandibular pheromone; QMP) which regulates many aspects of worker bee behavior and physiology. Forager honey bees are less responsive to QMP than young nurse bees engaged in brood care, suggesting that physiological changes associated with behavioral maturation may modulate response to this pheromone. Since cGMP is a major regulator of behavioral maturation in honey bee workers, we examined its role in modulating worker responses to QMP. Treatment with a cGMP analog, 8-Br-cGMP, resulted in significant reductions in both behavioral and physiological responses to QMP in young caged workers. Treatment significantly reduced attraction to QMP (the retinue response) and inhibited the QMP-mediated increase in vitellogenin levels in the fat bodies of worker bees. Genome-wide analysis of brain gene expression patterns demonstrated that cGMP has a larger effect on expression levels than QMP, and that QMP has specific effects in the presence of cGMP, suggesting that some responses to QMP may be dependent on an individual beesM-^R physiological state. Several functional gene categories were significantly differentially expressed, including genes involved in regulating GTPase activity, phototransduction, immunity, and carboxylic acid transmembrane transporter activity. Overall, our data suggest that cGMP-mediated processes play a large role in modulating responses to queen pheromone in honey bees, at the behavioral, physiological and molecular levels.
Project description:Our aim was to use next-generation sequencing to identify the miRNAs associated with caste determination in queen-destined and worker-destined larvae of the bumble bee, Bombus terrestris. We found that two miRNAs (miR-6001-5p and miR-6001-3p) were upregulated in queen-destined larvae that had passed the critical developmental period when caste becomes irreversible in this species. The two miRNAs form a duplex that is expressed from the gene VHDL, a homologue of Vitellogenin. This finding suggests a new connection between miRNAs and a key protein known to play multiple roles in regulating reproductive division of labour in eusocial Hymenoptera .
Project description:Our aims in this study were: 1) to identify the miRNAs of the bumble bees Bombus terrestris and B. impatiens; 2) to compare the total numbers of miRNAs between both bumble bee species and between them and the honey bee, Apis mellifera; and 3) to test whether the sequences and expression patterns of miRNAs were conserved between species. To investigate each of these aims we used miRNA-seq (deep sequencing of miRNA-enriched libraries) in B. terrestris, and bioinformatics prediction programs to identify miRNAs in both Bombus species. We identified 131 miRNAs in B. terrestris, and 114 in B. impatiens; of these, 17 were new miRNAs that had not previously been sequenced in any species. We found a striking level of difference in the miRNAs present between Bombus and A. mellifera, with 103 miRNAs in A. mellifera not being present in the genomes of the two bumble bees.