Domestication Effects on Stress Induced Steroid Secretion and Adrenal Gene Expression in Chickens

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.

Figure 1. Serum concentrations of (a) baseline pregnenolone and DHEA and (b) baseline and post-restraint levels of corticosterone in domestic White Leghorn (WL; n = 24) and wild Red Junglefowl (RJF; n = 24).

The values are given as mean ± SEM. The statistics for the figures is presented in Table 1.

Figure 2. Quantitative PCR (qPCR) analysis of StAR (a), CH25 (b), and POMC (c) mRNA expression in adrenals of White Leghorn (WL) and Red Junglefowl (RJF).

The adrenals were either collected at baseline or after 15 minutes restraint in a net. Results are shown as fold change after normalizing with TATA-binding protein and beta-2 Microglobulin mRNA. Each value represents the mean ± SEM. The statistics for the figures is presented in Table 1.

Figure 3. Quantitative PCR (qPCR) analysis of CYP17A1 (a), CYP19A1 (b), CYP21A2 (c) mRNA expression in adrenals of male and female White Leghorn (WL) and Red Junglefowl (RJF).

Results are shown as fold change after normalizing with TATA-binding protein and beta-2 Microglobulin mRNA. Each value represents the mean ± SEM. The statistics for the figures is presented in Table 1.