The Australian Wine Research Institute, Glen Osmond, South Australia, Australia.
School of Agriculture, Food and Wine, Faculty of Sciences, University of Adelaide, Adelaide, South Australia, Australia.
PLoS Genet. 2023 Mar 28;19(3):e1010692. doi: 10.1371/journal.pgen.1010692. eCollection 2023 Mar.
Copper tolerance and SO2 tolerance are two well-studied phenotypic traits of Saccharomyces cerevisiae. The genetic bases of these traits are the allelic expansion at the CUP1 locus and reciprocal translocation at the SSU1 locus, respectively. Previous work identified a negative association between SO2 and copper tolerance in S. cerevisiae wine yeasts. Here we probe the relationship between SO2 and copper tolerance and show that an increase in CUP1 copy number does not always impart copper tolerance in S. cerevisiae wine yeast. Bulk-segregant QTL analysis was used to identify variance at SSU1 as a causative factor in copper sensitivity, which was verified by reciprocal hemizygosity analysis in a strain carrying 20 copies of CUP1. Transcriptional and proteomic analysis demonstrated that SSU1 over-expression did not suppress CUP1 transcription or constrain protein production and provided evidence that SSU1 over-expression induced sulfur limitation during exposure to copper. Finally, an SSU1 over-expressing strain exhibited increased sensitivity to moderately elevated copper concentrations in sulfur-limited medium, demonstrating that SSU1 over-expression burdens the sulfate assimilation pathway. Over-expression of MET 3/14/16, genes upstream of H2S production in the sulfate assimilation pathway increased the production of SO2 and H2S but did not improve copper sensitivity in an SSU1 over-expressing background. We conclude that copper and SO2 tolerance are conditional traits in S. cerevisiae and provide evidence of the metabolic basis for their mutual exclusivity. These findings suggest an evolutionary driver for the extreme amplification of CUP1 observed in some yeasts.
铜耐受和 SO2 耐受是酿酒酵母中两个经过充分研究的表型特征。这些特征的遗传基础分别是 CUP1 基因座的等位基因扩展和 SSU1 基因座的相互易位。先前的工作确定了酿酒酵母葡萄酒酵母中 SO2 和铜耐受之间的负相关。在这里，我们研究了 SO2 和铜耐受之间的关系，并表明 CUP1 拷贝数的增加并不总是赋予酿酒酵母葡萄酒酵母铜耐受。 bulk-segregant QTL 分析用于鉴定 SSU1 中的变异作为铜敏感性的因果因素，这在携带 20 个 CUP1 拷贝的菌株中通过相互半合子分析得到了验证。转录组和蛋白质组分析表明，SSU1 过表达不会抑制 CUP1 转录或限制蛋白质产生，并提供证据表明 SSU1 过表达在暴露于铜时诱导硫限制。最后，一个 SSU1 过表达的菌株在硫限制培养基中对中等升高的铜浓度表现出更高的敏感性，表明 SSU1 过表达加重了硫酸盐同化途径的负担。硫酸盐同化途径中 H2S 产生上游基因 MET3/14/16 的过表达增加了 SO2 和 H2S 的产生，但在 SSU1 过表达背景下并没有改善铜敏感性。我们得出结论，铜和 SO2 耐受是酿酒酵母中的条件性状，并提供了它们相互排斥的代谢基础的证据。这些发现为一些酵母中观察到的 CUP1 极端扩增提供了进化驱动力。
