Gene expression can be modulated by epigenetic modifications, which may lead to a rapid adaptation to environmental stress. After stress cessation, changes in gene expression could be reversed, which would allow organisms to maintain their phenotype under transient environments, but this mechanism is poorly understood. Social stress downregulates a gene directly involved in pheomelanin synthesis (Slc7a11) by changing DNA m5C levels, avoiding cellular damage caused by stress.

Some organisms can modulate gene expression to trigger physiological responses that help adapt to environmental stress. The synthesis of the pigment pheomelanin in melanocytes seems to be one of these responses, as it may contribute to cellular homeostasis. Environmental oxidative stress was experimentally induced in male zebra finches Taeniopygia guttata by the administration of the herbicide diquat dibromide during feather growth to test if the expression of genes involved in pheomelanin...

Competitive environments promote high testosterone levels, oxidative stress and, consequently, impair cellular homeostasis. The regulation of genes involved in the synthesis of the pigment pheomelanin in melanocytes seems to help to maintain homeostasis against environmental oxidative stress. Here, social interactions in some zebra finch Taeniopygia guttata males were experimentally increased by keeping them in groups of six birds during feather growth, while others were kept alone, to test...

Cysteine plays essential biological roles, but excessive amounts produce cellular oxidative stress. Cysteine metabolism is mainly mediated by the enzymes cysteine dioxygenase and ?-glutamylcysteine synthetase, respectively coded by the genes CDO1 and GCLC. Here a new hypothesis is tested posing that the synthesis of the pigment pheomelanin also contributes to cysteine homeostasis in melanocytes, where cysteine can enter the pheomelanogenesis pathway.

Pheomelanin contributes to the pigmentation phenotype of animals by producing orange and light brown colours in the integument. However, pheomelanin synthesis in melanocytes requires consumption of glutathione (GSH), the most important intracellular antioxidant. Therefore, a genetic control favouring the production of large amounts of pheomelanin for pigmentation may lead to physiological costs under environmental conditions that promote oxidative stress. This possibility was investigated in...