Stress affects individuals under captivity. This could have been an important selection factor of adaptation to domestication, and it has been demonstrated that this adaptation could be acquired in few generations. The mechanism that generates stress is not clear, as well as if it could be transmissible through generations, although some advances have been made that showed that maternal behavior changes the epigenetic patterns of their descendants, producing stably inheritable alterations. In this paper, Lindqvist et al., used red junglefowl (RJF), the ancestor of domestic chickens, and domesticated white leghorn (WL) chickens, to show that the stress- induced learning is associated with a modification of gene expression in hypothalamus and pituitary. To this end, they subjected RJF (derived from a zoo population) and WL chickens to a chronic mild stressful treatment in the parental generation, and then both progenitors and descendants were selected for learning and competition tests. Parental WL birds took more tests to reach the solving criteria, while RJF and unstressed birds did it faster. Thus, the treatment affected the learning capacity. On the other hand, chicks from stressed WL parents were slower than descendants of control birds in another learning test (although no significant differences were found with RJF offspring). A modification of the weight was also observed in the WL offspring, and the data suggested to the authors that it is a consequence of the stressful environment. Later, as hypothalamus and pituitary are the centers of stress in the body, they hypothesized that this behavior could be due to differential gene expression patterns in these organs, and using microarrays they found a correlation both in WL parental and offspring, but not in RJF, and from this they concluded that:
Lindqvist C. et al. 2007. PLoS One 4:e364
epigenetics
[...] the regulatory change induced by stress was transferred to the offspring in WL, while there was no transfer between generations in RJF [...]Comment: A difference expression is seen, but neither "transgenerational inheritance" nor any other "transfer" mechanism was measured. Alterations in gene expression could be due to many factors that Lindqvist et al., have not evaluated. In any case, these observations should motivate further investigations that hopefully will explain why stress responses could be passed through generations of poultry, as it has already been observed and discussed here before for other organisms.
Lindqvist C. et al. 2007. PLoS One 4:e364
epigenetics
