title: Differential gene expression between hygienic and non-hygienic honeybee (Apis mellifera L.) hives.
abstract: BACKGROUND
  Hygienic behavior is a complex, genetically-based quantitative trait that serves as a key defense mechanism against parasites and diseases in Apis mellifera. Yet, the genomic basis and functional pathways involved in the initiation of this behavior are still unclear. Deciphering the genomic basis of hygienic behavior is a prerequisite to developing an extensive repertoire of genetic markers associated to the performance level of this quantitative trait. To fill this knowledge gap, we performed an RNA-seq on brain samples of 25 honeybees per hives from five hygienic and three non-hygienic hives.
  
  
  RESULTS
  This analysis revealed that a limited number of functional genes are involved in honeybee hygienic behavior. The genes identified, and especially their location in the honeybee genome, are consistent with previous findings. Indeed, the genomic sequences of most differentially expressed genes were found on the majority of the QTL regions associated to the hygienic behavior described in previous studies. According to the Gene Ontology annotation, 15 genes are linked to the GO-terms DNA or nucleotide binding, indicating a possible role of these genes in transcription regulation. Furthermore, GO-category enrichment analysis revealed that electron carrier activity is over-represented, involving only genes belonging to the cytochrome P450. Cytochrome P450 enzymes' overexpression can be explained by a disturbance in the regulation of expression induced by changes in transcription regulation or sensitivity to xenobiotics. Over-expressed cytochrome P450 enzymes could potentially degrade the odorant pheromones or chemicals that normally signal the presence of a diseased brood before activation of the removal process thereby inhibit hygienic behavior.
  
  
  CONCLUSIONS
  These findings improve our understanding on the genetics basis of the hygienic behavior. Our results show that hygienic behavior relies on a limited set of genes linked to different regulation patterns (expression level and biological processes) associated with an over-expression of cytochrome P450 genes.
authors.affiliation: Institut de Biologie Intégrative et des Systèmes (IBIS), Université Laval, Pavillon Charles-Eugène Marchand, bureau 1253, 1030, Avenue de la Médecine, G1V 0A6, Québec, QC, Canada. sebastien.boutin.1@ulaval.ca.
authors.forename: Sébastien
authors.initials: S
authors.lastname: Boutin
authors.affiliation: Institut de Biologie Intégrative et des Systèmes (IBIS), Université Laval, Pavillon Charles-Eugène Marchand, bureau 1253, 1030, Avenue de la Médecine, G1V 0A6, Québec, QC, Canada. mohamed.alburaki.1@ulaval.ca.|Entomology and Plant Pathology Department, West TN Research and Education Center, The University of Tennessee, 605 Airways Blvd, Jackson, TN, 38301, USA. mohamed.alburaki.1@ulaval.ca.
authors.forename: Mohamed
authors.initials: M
authors.lastname: Alburaki
authors.affiliation: Institut de Biologie Intégrative et des Systèmes (IBIS), Université Laval, Pavillon Charles-Eugène Marchand, bureau 1253, 1030, Avenue de la Médecine, G1V 0A6, Québec, QC, Canada. pierre-luc.mercier.1@ulaval.ca.
authors.forename: Pierre-Luc
authors.initials: PL
authors.lastname: Mercier
authors.affiliation: Département de biologie, Faculté des sciences et de genie, Université Laval, Québec, Canada. pierre.giovenazzo@bio.ulaval.ca.
authors.forename: Pierre
authors.initials: P
authors.lastname: Giovenazzo
authors.affiliation: Institut de Biologie Intégrative et des Systèmes (IBIS), Université Laval, Pavillon Charles-Eugène Marchand, bureau 1253, 1030, Avenue de la Médecine, G1V 0A6, Québec, QC, Canada. nicolas.derome@bio.ulaval.ca.|Département de biologie, Faculté des sciences et de genie, Université Laval, Québec, Canada. nicolas.derome@bio.ulaval.ca.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Derome
mesh_terms: D000818:Animals; D001516:Bees / Q000235:genetics*; D001522:Behavior, Animal; D001921:Brain / Q000378:metabolism; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics; D005786:Gene Expression Regulation / Q000235:genetics*; D063990:Gene Ontology; D005819:Genetic Markers / Q000235:genetics; D049750:Genome, Insect / Q000235:genetics*; D058977:Molecular Sequence Annotation / Q000379:methods; D012919:Social Behavior; D014158:Transcription, Genetic / Q000235:genetics
chemical_list: D005819:Genetic Markers; D003577:Cytochrome P-450 Enzyme System