title: Domestication and tameness: brain gene expression in red junglefowl selected for less fear of humans suggests effects on reproduction and immunology.
abstract: The domestication of animals has generated a set of phenotypic modifications, affecting behaviour, appearance, physiology and reproduction, which are consistent across a range of species. We hypothesized that some of these phenotypes could have evolved because of genetic correlation to tameness, an essential trait for successful domestication. Starting from an outbred population of red junglefowl, ancestor of all domestic chickens, we selected birds for either high or low fear of humans for five generations. Birds from the fifth selected generation (S5) showed a divergent pattern of growth and reproduction, where low fear chickens grew larger and produced larger offspring. To examine underlying genetic mechanisms, we used microarrays to study gene expression in thalamus/hypothalamus, a brain region involved in fear and stress, in both the parental generation and the S5. While parents of the selection lines did not show any differentially expressed genes, there were a total of 33 genes with adjustedp-values below 0.1 in S5. These were mainly related to sperm-function, immunological functions, with only a few known to be relevant to behaviour. Hence, five generations of divergent selection for fear of humans produced changes in hypothalamic gene expression profiles related to pathways associated with male reproduction and to immunology. This may be linked to the effects seen on growth and size of offspring. These results support the hypothesis that domesticated phenotypes may evolve because of correlated effects related to reduced fear of humans.
authors.affiliation: AVIAN Behavioural Genomics and Physiology group, IFM Biology , Linköping University , 58183 Linköping , Sweden.
authors.forename: Johan
authors.identifier: 0000-0001-5508-4465
authors.initials: J
authors.lastname: Bélteky
authors.affiliation: AVIAN Behavioural Genomics and Physiology group, IFM Biology , Linköping University , 58183 Linköping , Sweden.
authors.forename: Beatrix
authors.initials: B
authors.lastname: Agnvall
authors.affiliation: AVIAN Behavioural Genomics and Physiology group, IFM Biology , Linköping University , 58183 Linköping , Sweden.
authors.forename: Martin
authors.initials: M
authors.lastname: Johnsson
authors.affiliation: AVIAN Behavioural Genomics and Physiology group, IFM Biology , Linköping University , 58183 Linköping , Sweden.
authors.forename: Dominic
authors.initials: D
authors.lastname: Wright
authors.affiliation: AVIAN Behavioural Genomics and Physiology group, IFM Biology , Linköping University , 58183 Linköping , Sweden.
authors.forename: Per
authors.initials: P
authors.lastname: Jensen
keywords: artificial selection; chicken; fearfulness; gene expression; microarray