Unknown,Transcriptomics,Genomics,Proteomics

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Transcription profiling of honey bee brain and ovary reveals pheromone response is correlated with reproductive traits and brain gene expression in individual honey bees

ABSTRACT: In honey bees (Apis mellifera), the reproductive queen produces a pheromonal signal that regulates many aspects of worker behavior and physiology and is critical for maintaining colony organization. Queen mandibular pheromone (QMP) inhibits worker reproduction, attracts workers from a short distance (retinue response), inhibits the rearing of new queens, modulates age-related division of labor and globally alters brain gene expression in worker bees. Interestingly, substantial variation in worker retinue responses to QMP has been found between colonies, but the molecular and physiological bases for variation in individual responses to the queen have not been characterized. Here, we demonstrate that individual retinue response is negatively correlated with traits associated with reproductive potential. Workers with low response to QMP have more ovarioles and higher levels of vitellogenin transcripts than workers with a high response to QMP, suggesting that workers with greater reproductive potential may be attempting to escape queen control. Retinue response appears to be associated with a suite of behavioral and physiological traits that may be pleiotropically linked. However, while these phenotypes are all correlated at the organismal level, the underlying brain expression patterns and gene networks associated with each trait are independent, suggesting that these phenotypes are uncoupled at the molecular level in adult bees. These studies provide insights into the ultimate and proximate causes of natural variation in pheromone response in honey bees.

ORGANISM(S): Apis mellifera

SUBMITTER: Christina Grozinger

PROVIDER: E-MEXP-1724 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Honeybees are very important eusocial insects and are involved in the pollination of many plants. Queen bees and worker bees develop from the same fertilized eggs, and are thus genetically identical despite their substantial behavioural and physiological differences. The mechanism governing developmental differences between worker and queen bees has always attracted much interest. While there are several reports on mRNA expression related to caste differentiation, no systematic investigation of small RNAs has thus far been carried out. Results: Using deep sequencing we systematically profiled small RNA expression in 4th-6th day worker larvae and queen larvae (the critical stages at which the fates of workers and queens are determined), and found that 38 miRNAs were differentially expressed between worker and queen larvae. In addition, 639 mature miRNA candidates were identified in our work for the first time, of which, 526 were expressed only in workers (318) or queens (208). Conclusion: We present the first profile of honeybee small RNAs and explore the mechanism of caste differentiation between worker and queen bees. Caste-specific expression patterns and large discrepancies in small RNA profiles between worker and queen bees indicate that small RNAs may be related to the differential development of worker and queen bee larvae. Results presented here will make a valuable contribution to understanding the caste switch between worker and queen bees. Three healthy 10-frame colonies of ‘Zhenongda No.1’- a high-yielding royal jelly breed of Apis mellifera ligustica , were maintained at the Huajiachi campus of Zhejiang University. In each colony, the queen laid eggs over a period of 24 hours in one empty frame which was subsequently moved to an egg-free super-chamber. After 66 hours (less than 18 hours after hatching), we transferred 150 larvae into queen cups to rear queens in each colony and put the queen cup frames into their corresponding colonies. 40-60 worker larvae and queen larvae were collected from each colony after 4 days (73~90 h after hatching), 5 days (97~114 h after hatching) and 6 days (121~138 h after hatching). The larval samples were collected into 50 ml tubes, immediately frozen in liquid nitrogen and stored at -80C until being used for RNA extraction. After total RNA was extracted and quantified , relative equal amounts of total RNAs from each of the three sampling days were pooled into respectively worker and queen samples, and the fraction of small RNAs less than 30nt long was retained and sequenced on the Illumina/Solexa high-throughput platform (HTP).

Project description:BACKGROUND: Social insects, such as honey bees, use molecular, physiological and behavioral responses to combat pathogens and parasites. The honey bee genome contains all of the canonical insect immune response pathways, and several studies have demonstrated that pathogens can activate expression of immune effectors. Honey bees also use behavioral responses, termed social immunity, to collectively defend their hives from pathogens and parasites. These responses include hygienic behavior (where workers remove diseased brood) and allo-grooming (where workers remove ectoparasites from nestmates). We have previously demonstrated that immunostimulation causes changes in the cuticular hydrocarbon profiles of workers, which results in altered worker-worker social interactions. Thus, cuticular hydrocarbons may enable workers to identify sick nestmates, and adjust their behavior in response. Here, we test the specificity of behavioral, chemical and genomic responses to immunostimulation by challenging workers with a panel of different immune stimulants (saline, Sephadex beads and Gram-negative bacteria E. coli). RESULTS: While only bacteria-injected bees elicited altered behavioral responses from healthy nestmates compared to controls, all treatments resulted in significant changes in cuticular hydrocarbon profiles. Immunostimulation caused significant changes in expression of hundreds of genes, the majority of which have not been identified as members of the canonical immune response pathways. Furthermore, several new candidate genes that may play a role in cuticular hydrocarbon biosynthesis were identified. Finally, we identified common genes regulated by pathogen challenge in honey bees and other insects, suggesting that immune responses are conserved at the molecular level. CONCLUSIONS: These studies suggest that honey bee genomic responses to immunostimulation are substantially broader than expected, and may mediate the behavioral changes associated with social immunity by orchestrating changes in chemical signaling.

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Transcription profiling of honey bee brain and ovary reveals pheromone response is correlated with reproductive traits and brain gene expression in individual honey bees

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