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...基因Slc7a11的表达可通过为细胞提供可用于合成谷胱甘肽（glutathione, GSH）——细胞内最重要的抗氧化物质——的半胱氨酸，提升细胞的抗氧化能力。在黑素细胞（melanocytes）中，细胞内的半胱氨酸还可进入黑素体（melanosomes），并参与色素褐黑素（pheomelanin）的合成通路，由此减少可用于GSH合成的半胱氨酸供应量，进而可能引发慢性氧化应激（oxidative stress）。据此我们提出假说：在存在氧化应激的环境条件下，存在一种限制黑素细胞内半胱氨酸用于褐黑素合成的机制，该机制可能具有生理优势，并会受到自然选择的青睐。本研究通过比较两类捕食风险（氧化应激的天然来源）存在差异的种群的欧亚䴓（Eurasian nuthatch，学名Sitta europaea）发育中的雏鸟，分析黑素细胞Slc7a11的表达对基于褐黑素的体色的影响，以此寻找上述机制的相关证据。褐黑素合成及……