Heritability, environmental effects, and genetic and phenotypic correlations of oxidative stress resistance-related enzyme activities during early life stages in Atlantic salmon

Oxidative stress (OS) may pose important physiological constraints on individuals, affecting trade-offs between growth and reproduction or ageing and survival. Despite such evolutionary and ecological importance, the results from studies on the magnitude of individual variation in OS resistance and the underlying causes of this variation such as genetic, environmental, and maternal origins, remain inconclusive. Using a high throughput methodology, we investigated the activity levels in three OS resistance-related enzymes (superoxide dismutase, SOD; glutathione reductase, GR; glutathione S-transferase, GST) during the early life stages of 1000 individuals from 50 paternal half-sib families in two populations of Atlantic salmon. Using animal mixed models, we detected the presence of narrow-sense heritability for SOD and GST; that for GST differed between populations due to differences in environmental variance. We found support for the presence of common environmental variation, including maternal effects, for only GR. Using a bivariate animal model, we detected a positive environmental correlation between activity levels of SOD and GST but were unable to detect an additive genetic correlation. Our results complement previous heritability findings for levels of reactive oxygen species or OS resistance by demonstrating the presence of heritability for OS-related enzyme activities. Our findings provide a foundation for future work, such as investigations on the evolutionary importance of variation in enzyme activities. In addition, our findings emphasise the importance of accounting for developmental stage, environmental variance, and kin relationships when investigating the OS-response at the enzyme activity level.

氧化应激（Oxidative stress, OS）可对个体产生重要的生理约束，影响其生长与繁殖、衰老与存活之间的权衡。尽管氧化应激在进化与生态层面具有关键意义，但目前针对个体氧化应激抗性差异的程度，以及该差异的潜在成因（包括遗传、环境与母体来源）的相关研究，结论仍未达成统一。本研究采用高通量实验方法，对两个种群大西洋鲑中，来自50个父系半同胞家系的1000个个体的早期发育阶段体内的三种氧化应激抗性相关酶活性水平进行了检测：超氧化物歧化酶（superoxide dismutase, SOD）、谷胱甘肽还原酶（glutathione reductase, GR）以及谷胱甘肽S-转移酶（glutathione S-transferase, GST）。通过动物混合模型分析，我们检测到SOD与GST的活性存在狭义遗传力；其中GST活性的狭义遗传力因种群而异，这源于不同种群间的环境方差差异。我们仅在GR的活性中，发现了包括母体效应在内的共同环境变异的相关证据。采用双变量动物模型分析，我们检测到SOD与GST的活性之间存在正向环境相关，但未发现显著的加性遗传相关。本研究证实了氧化应激相关酶活性存在遗传力，补充了此前关于活性氧水平或氧化应激抗性的遗传力相关研究成果。本研究结果为后续相关研究奠定了基础，例如探究酶活性差异的进化重要性。此外，本研究强调，在以酶活性水平探究氧化应激响应时，需考虑发育阶段、环境方差以及亲缘关系等因素的影响。