Hanson Katherine M, Long Anthony D, Macdonald Stuart J
Department of Molecular Biosciences and Center for Genomics, University of Kansas, 1200 Sunnyside Avenue, Lawrence, KS 66045, USA.
Department of Ecology and Evolutionary Biology, University of California at Irvine, Irvine, CA 92697, USA.
bioRxiv. 2025 Jun 19:2025.06.12.659401. doi: 10.1101/2025.06.12.659401.
Heavy metals are a widespread environmental contaminant, and even low levels of some metals can disrupt cellular processes and result in DNA damage. However, the consequences of metal exposure are variable among individuals, with susceptibility to metal toxicity representing a complex trait influenced by genetic and non-genetic factors. To uncover toxicity response genes, and better understand responses to metal toxicity, we sought to dissect resistance to zinc, a metal required for normal cellular function, which can be toxic at high doses. To facilitate efficient, powerful discovery of Quantitative Trait Loci (QTL) we employed extreme, or X-QTL mapping, leveraging a multiparental, recombinant population. Our approach involved bulk selection of zinc-resistant individuals, sequencing several replicate pools of selected and control animals, and identified QTL as genomic positions showing consistent allele frequency shifts between treatments. We successfully identified seven regions segregating for resistance/susceptibility alleles, and implicated several strong candidate genes. Phenotypic characterization of populations derived from selected or control animals revealed that our selection procedure resulted in greater egg-to-adult emergence, and a reduced developmental delay on zinc media. We subsequently measured emergence and development time for a series of midgut-specific RNAi gene knockdowns and matched genetic controls raised in both zinc-supplemented and normal media. This identified ten genes with significant genotype-by-treatment effects, including , which encodes a zinc sensor protein. Our work highlights recognized and novel contributors to zinc toxicity resistance in flies, and provides a pathway to a broader understanding of the biological impact of metal toxicity.
重金属是一种广泛存在的环境污染物，即使是某些金属的低含量也会扰乱细胞过程并导致DNA损伤。然而，个体对金属暴露的后果各不相同，对金属毒性的易感性是一种受遗传和非遗传因素影响的复杂性状。为了发现毒性反应基因，并更好地理解对金属毒性的反应，我们试图剖析对锌的抗性，锌是正常细胞功能所需的一种金属，高剂量时可能有毒。为了促进对数量性状位点（QTL）的高效、有力发现，我们采用了极端或X-QTL定位方法，利用了一个多亲本重组群体。我们的方法包括大量选择抗锌个体，对选定和对照动物的几个重复样本进行测序，并将QTL确定为在处理之间显示一致等位基因频率变化的基因组位置。我们成功地鉴定出了七个区分抗性/敏感等位基因的区域，并确定了几个强有力的候选基因。对来自选定或对照动物群体的表型特征分析表明，我们的选择程序导致了更高的从卵到成虫的羽化率，并减少了在锌培养基上的发育延迟。随后，我们测量了一系列中肠特异性RNAi基因敲除以及在补充锌和正常培养基中培养的匹配遗传对照的羽化率和发育时间。这确定了十个具有显著基因型-处理效应的基因，包括编码锌传感蛋白的基因。我们的工作突出了果蝇中已知的和新发现的对锌毒性抗性的贡献因素，并为更广泛地理解金属毒性的生物学影响提供了一条途径。
