Department of Biological Sciences, Macquarie University, Sydney, NSW 2109, Australia.
Department of Environmental Sciences, Macquarie University, Sydney, NSW 2109, Australia.
Sci Total Environ. 2019 Feb 10;650(Pt 1):679-686. doi: 10.1016/j.scitotenv.2018.09.052. Epub 2018 Sep 5.
Metals and metalloids at elevated concentrations can be toxic to both humans and wildlife. In particular, lead exposure can act as a stressor to wildlife and cause negative effects on fitness. Any ability to adapt to stress caused by the negative effects of trace metal exposure would be beneficial for species living in contaminated environments. However, mechanisms for responding adaptively to metal contamination are not fully understood in free-living organisms. The Australian populations of the house sparrow (Passer domesticus) provides an excellent opportunity to study potential adaptation to environmental lead contamination because they have a commensal relationship with humans and are distributed broadly across Australian settlements including many long-term mining and smelting communities. To examine the potential for an evolutionary response to long-term lead exposure, we collected genomic SNP data using the house sparrow 200 K SNP array, from 11 localities across the Australian distribution including two mining sites (Broken Hill and Mount Isa, which are two genetically independent populations) that have well-established elevated levels of lead contamination as well as trace metals and metalloids. We contrast these known contaminated locations to other lesser-contaminated environments. Using an ecological association genome scan method to identify genomic differentiation associated with estimates of lead contamination we identified 60 outlier loci across three tests. A total of 39 genes were found to be physically linked (within 20 kbps) of all outliers in the house sparrow reference genome. The linked candidate genes included 12 genes relevant to lead exposure, such as two metal transporters that can transport metals including lead and zinc across cell membranes. These candidate genes provide targets for follow up experiments comparing resilience to lead exposure between populations exposed to varied levels of lead contamination.
金属和类金属在浓度升高时可能对人类和野生动物都有毒性。特别是，铅暴露可能成为野生动物的应激源，并对其适应性产生负面影响。任何适应由于痕量金属暴露而产生的应激的能力对生活在污染环境中的物种都是有益的。然而，在自由生活的生物中，对金属污染做出适应性反应的机制还不完全清楚。澳大利亚的家麻雀（Passer domesticus）种群为研究潜在的适应环境铅污染提供了极好的机会，因为它们与人类共生，广泛分布于澳大利亚的定居点，包括许多长期采矿和冶炼社区。为了研究对长期铅暴露的潜在进化反应，我们使用家麻雀 200K SNP 芯片收集了基因组 SNP 数据，这些样本来自澳大利亚分布范围内的 11 个地点，包括两个采矿地点（Broken Hill 和 Mount Isa，它们是两个遗传上独立的种群），那里有成熟的高铅污染以及痕量金属和类金属。我们将这些已知的污染地点与其他污染程度较低的环境进行了对比。使用生态关联基因组扫描方法，我们根据铅污染的估计值来识别与基因组分化相关的基因座，在三种测试中发现了 60 个异常值基因座。在麻雀参考基因组中，总共发现了 39 个基因与所有异常值的物理位置相关（在 20kbp 内）。这些连锁的候选基因包括 12 个与铅暴露相关的基因，例如两种金属转运蛋白，可以将金属（包括铅和锌）穿过细胞膜进行转运。这些候选基因为后续实验提供了目标，以比较暴露于不同水平铅污染的种群对铅暴露的恢复能力。
