Abstract
Understanding the genetic basis of phenotypic diversity is a challenge in contemporary biology. Domestication provides a model for unravelling aspects of the genetic basis of stress sensitivity. The ancestral Red Junglefowl (RJF) exhibits greater fear-related behaviour and a more pronounced HPA-axis reactivity than its domesticated counterpart, the White Leghorn (WL). By comparing hormones (plasmatic) and adrenal global gene transcription profiles between WL and RJF in response to an acute stress event, we investigated the molecular basis for the altered physiological stress responsiveness in domesticated chickens. Basal levels of pregnenolone and dehydroepiandrosterone as well as corticosterone response were lower in WL. Microarray analysis of gene expression in adrenal glands showed a significant breed effect in a large number of transcripts with over-representation of genes in the channel activity pathway. The expression of the best-known steroidogenesis genes were similar across the breeds used. Transcription levels of acute stress response genes such as StAR, CH25 and POMC were upregulated in response to acute stress. Dampened HPA reactivity in domesticated chickens was associated with changes in the expression of several genes that presents potentially minor regulatory effects rather than by means of change in expression of critical steroidogenic genes in the adrenal.
Highlights
The primary physiological stress response in general is an increase in HPA-axis activity, which results in elevated levels of the glucocorticoids that regulate metabolism
We investigate the possibility that domestication may have modified the stress responses of chickens by targeting genes involved in the steroidogenic pathway in the adrenals
The basal levels of PREG and DHEA were significantly higher in Red Junglefowl (RJF) (Table 1) but there was no significant difference between White Leghorn (WL) and RJF in baseline levels of CORT
Summary
The primary physiological stress response in general is an increase in HPA-axis activity, which results in elevated levels of the glucocorticoids that regulate metabolism. We investigate the possibility that domestication may have modified the stress responses of chickens by targeting genes involved in the steroidogenic pathway in the adrenals. This should lead to modified stress levels of several steroids that could be detected by identifying altered genetic functions that are related to steroidogenesis. The aim of the current study was to evaluate the effects of domestication on acute stress sensitivity of chickens at both molecular and hormonal levels This was achieved by studying adrenal gene expression at baseline and after restraint stress in six weeks old domesticated White Leghorns and ancestral Red Junglefowl using microarrays and quantitative PCR. The plasma levels of three central steroids with adrenal origin, pregnenolone (PREG), dehydroepiandrosterone (DHEA), and corticosterone (CORT) were compared in the same animals
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