Differential influence of Slc7a11 expression and body condition on pheomelanin‐based pigmentation in two Eurasian nuthatch Sitta europaea populations with different predation risk

The expression of the gene Slc7a11promotes the antioxidant capacity of cells by providing them with cysteine that can be used for the synthesis of glutathione (GSH), the most important intracellular antioxidant. In melanocytes, intracellular cysteine can also enter melanosomes and get incorporated in the pigment pheomelanin synthesis pathway, thus decreasing cysteine availability for GSH synthesis and potentially creating chronic oxidative stress. We thus hypothesized that a mechanism limiting the use of intramelanocytic cysteine for pheomelanin synthesis in environmental conditions generating oxidative stress may be physiologically advantageous and favored by natural selection. Here we searched for evidence of such a mechanism by comparing the influence of melanocytic Slc7a11expression on pheomelanin-based pigmentation in developing Eurasian nuthatch Sitta europaeanestlings from two populations differing in predation risk, a natural source of oxidative stress. Pheomelanin synthesis and...