The transcription factor Krüppel homolog 1 is linked to hormone mediated social organization in bees

<p>Abstract</p> <p>Background</p> <p>Regulation of worker behavior by dominant queens or workers is a hallmark of insect societies, but the underlying molecular mechanisms and their evolutionary conservation are not well understood. Honey bee and bumble bee colonies consist of a single reproductive queen and facultatively sterile workers. The queens' influences on the workers are mediated largely via inhibition of juvenile hormone titers, which affect division of labor in honey bees and worker reproduction in bumble bees. Studies in honey bees identified a transcription factor, <it>Krüppel-homolog 1 </it>(<it>Kr-h1</it>), whose expression in worker brains is significantly downregulated in the presence of a queen or queen pheromone and higher in forager bees, making this gene an ideal candidate for examining the evolutionary conservation of socially regulated pathways in Hymenoptera.</p> <p>Results</p> <p>In contrast to honey bees, bumble bees foragers do not have higher <it>Kr-h1 </it>levels relative to nurses: in one of three colonies levels were similar in nurses and foragers, and in two colonies levels were higher in nurses. Similarly to honey bees, brain <it>Kr-h1 </it>levels were significantly downregulated in the presence versus absence of a queen. Furthermore, in small queenless groups, <it>Kr-h1 </it>levels were downregulated in subordinate workers with undeveloped ovaries relative to dominant individuals with active ovaries. Brain <it>Kr-h1 </it>levels were upregulated by juvenile hormone treatment relative to a vehicle control. Finally, phylogenetic analysis indicates that KR-H1 orthologs are presence across insect orders. Though this protein is highly conserved between honey bees and bumble bees, there are significant differences between orthologs of insects from different orders.</p> <p>Conclusions</p> <p>Our results suggest that <it>Kr-h1 </it>is associated with juvenile hormone mediated regulation of reproduction in bumble bees. The expression of this transcription factor is inhibited by the queen and associated with endocrine mediated regulation of social organization in two species of bees. Thus, KR-H1 may transcriptionally regulate a conserved genetic module that is part of a pathway that has been co-opted to function in social behavior, and adjusts the behavior of workers to their social environmental context.</p

Honey bee neurogenomic responses to affiliative and agonistic social interactions

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/147835/1/gbb12509-sup-0003-FigureS3.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/147835/2/gbb12509-sup-0002-FigureS2.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/147835/3/gbb12509-sup-0001-FigureS1.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/147835/4/gbb12509.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/147835/5/gbb12509_am.pd

Cross‐species systems analysis of evolutionary toolkits of neurogenomic response to social challenge

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/147855/1/gbb12502.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/147855/2/gbb12502-sup-0002-TableS1.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/147855/3/gbb12502_am.pd

The genomes of two key bumblebee species with primitive eusocial organization

Background: The shift from solitary to social behavior is one of the major evolutionary transitions. Primitively eusocial bumblebees are uniquely placed to illuminate the evolution of highly eusocial insect societies. Bumblebees are also invaluable natural and agricultural pollinators, and there is widespread concern over recent population declines in some species. High-quality genomic data will inform key aspects of bumblebee biology, including susceptibility to implicated population viability threats. Results: We report the high quality draft genome sequences of Bombus terrestris and Bombus impatiens, two ecologically dominant bumblebees and widely utilized study species. Comparing these new genomes to those of the highly eusocial honeybee Apis mellifera and other Hymenoptera, we identify deeply conserved similarities, as well as novelties key to the biology of these organisms. Some honeybee genome features thought to underpin advanced eusociality are also present in bumblebees, indicating an earlier evolution in the bee lineage. Xenobiotic detoxification and immune genes are similarly depauperate in bumblebees and honeybees, and multiple categories of genes linked to social organization, including development and behavior, show high conservation. Key differences identified include a bias in bumblebee chemoreception towards gustation from olfaction, and striking differences in microRNAs, potentially responsible for gene regulation underlying social and other traits. Conclusions: These two bumblebee genomes provide a foundation for post-genomic research on these key pollinators and insect societies. Overall, gene repertoires suggest that the route to advanced eusociality in bees was mediated by many small changes in many genes and processes, and not by notable expansion or depauperation

Laboratory Assay of Brood Care for Quantitative Analyses of Individual Differences in Honey Bee (Apis mellifera) Affiliative Behavior.

Care of offspring is a form of affiliative behavior that is fundamental to studies of animal social behavior. Insects do not figure prominently in this topic because Drosophila melanogaster and other traditional models show little if any paternal or maternal care. However, the eusocial honey bee exhibits cooperative brood care with larvae receiving intense and continuous care from their adult sisters, but this behavior has not been well studied because a robust quantitative assay does not exist. We present a new laboratory assay that enables quantification of group or individual honey bee brood "nursing behavior" toward a queen larva. In addition to validating the assay, we used it to examine the influence of the age of the larva and the genetic background of the adult bees on nursing performance. This new assay also can be used in the future for mechanistic analyses of eusociality and comparative analyses of affilative behavior with other animals

Worker response to a queen cell with a larva vs. an empty cell.

<p>Number of visits (inspections and nursing, A and B), total time spent visiting (C and D) and number of bees visiting cell (E and F), for bees from Colony 1 (A, C, E) and Colony 2 (B, D, F). Data represent average ± SE, sample size (number of groups) is at the base of each bar, p-values summarize the results of paired t-test (A: <i>t</i>_<i>(8)</i> = 6.4; B: <i>t</i>_<i>(8)</i> = 7.1; C: <i>t</i>_<i>(8)</i> = 3.4; D: <i>t</i>_<i>(9)</i> = 3.0; E: <i>t</i>_<i>(9)</i> = 5.3; F: <i>t</i>_<i>(9)</i> = 3.1).</p

Effect of adult worker genetic background on nursing behavior.

<p>Bees from three genetically different colonies were studied. Latency until first cell visit (A); total number of inspection visits (B); total number of nursing visits (C); total time spent visiting larvae (D); and number of bees visiting cell (E). The p-value summarizes the results of one-way ANOVA (F₍₂₎ ≥ 10.4 for all measurements), different letter above the bars indicate significant pair-wise differences in LSD post-hoc test (p < 0.05).</p

Effect of group size on nursing performances.

<p>Percentage of: cells with cocoons or capped / total number of queen cells tested (left); queens that eclosed / total number of queen cells (middle); and queens that eclosed / cells with cocoon or capped (right) in three experimental groups: 8-bees (blue; N = 65), single-bee (green; N = 38) and zero-bees (yellow; N = 24). The p-values summarize the results of Fisher’s exact test for independence, different letters in parentheses indicate a significant difference in proportion between the groups in a pairwise test (Fisher's exact test with Bonferroni correction for multiple testing p < 0.05).</p

Worker response to a queen cell with only larva vs. a queen cell with royal jelly.

<p>Number of visits (A), total time spent visiting (B) and number of bees visiting cell (C). Scan sampling of 21 groups (10 bees in each group) during the first 5 minutes after the introduction of either a queen larva or royal jelly. Data represent average ± SE, sample size (number of groups) is at the base of each bar, p-values summarize the results of paired t-test (A: <i>t</i>_<i>(20)</i> = 2.5; B: <i>t</i>_<i>(20)</i> = 2.9; C: <i>t</i>_<i>(20)</i> = 3.25).</p