title: Behavioral and molecular studies of quantitative differences in hygienic behavior in honeybees.
abstract: BACKGROUND
  Hygienic behavior (HB) enables honeybees to tolerate parasites, including infection with the parasitic mite Varroa destructor, and it is a well-known example of a quantitative genetic trait. The understanding of the molecular processes underpinning the quantitative differences in this behavior remains limited.
  
  
  RESULTS
  We performed gene expression studies in worker bees that displayed quantitative genetic differences in HB. We established a high and low genetic source of HB performance and studied the engagements into HB of single worker bees under the same environmental conditions. We found that the percentage of worker bees that engaged in a hygienic behavioral task tripled in the high versus low HB sources, thus suggesting that genetic differences may mediate differences in stimulated states to perform HB. We found 501 differently expressed genes (DEGs) in the brains of hygienic and non-hygienic performing workers in the high HB source bees, and 342 DEGs in the brains of hygienic performing worker bees, relative to the gene expression in non-hygienic worker bees from the low HB source group. "Cell surface receptor ligand signal transduction" in the high and "negative regulation of cell communication" in the low HB source were overrepresented molecular processes, suggesting that these molecular processes in the brain may play a role in the regulation of quantitative differences in HB. Moreover, only 21 HB-associated DEGs were common between the high and low HB sources.
  
  
  CONCLUSIONS
  The better HB colony performance is primarily achieved by a high number of bees engaging in the hygienic tasks that associate with distinct molecular processes in the brain. We propose that different gene products and pathways may mediate the quantitative genetic differences of HB.
authors: Institute of Evolutionary Genetics, Heinrich Heine University Duesseldorf, Universitaetsstrasse 1, 40225, Duesseldorf, Germany.
authors: Tanja
authors: T
authors: Gempe
authors: Institute for Bee Research Hohen Neuendorf, Friedrich-Engels-Strasse 32, 16540, Hohen Neuendorf, Germany.|, Fischerweg 5, 2503, Biel, Switzerland.
authors: Silke
authors: S
authors: Stach
authors: Institute for Bee Research Hohen Neuendorf, Friedrich-Engels-Strasse 32, 16540, Hohen Neuendorf, Germany.
authors: Kaspar
authors: K
authors: Bienefeld
authors: Institute of Evolutionary Genetics, Heinrich Heine University Duesseldorf, Universitaetsstrasse 1, 40225, Duesseldorf, Germany.
authors: Marianne
authors: M
authors: Otte
authors: Institute of Evolutionary Genetics, Heinrich Heine University Duesseldorf, Universitaetsstrasse 1, 40225, Duesseldorf, Germany. martin.beye@hhu.de.
authors: Martin
authors: M
authors: Beye
mesh_terms: D000818:Animals; D001516:Bees / Q000502:physiology*; D001522:Behavior, Animal; D001921:Brain / Q000502:physiology; D006920:Hygiene
keywords: Gene expression; Hygienic behavior (HB); Quantitative genetic trait; Varroa; Varroa sensitive hygiene (VSH)