Chhoker Kamaldeep, Hausner Georg, Harris Steven D
Department of Biological Sciences, University of Manitoba, Winnipeg, MB, Canada, R3T 2N2.
Department of Microbiology, University of Manitoba, Winnipeg, MB, Canada, R3T 2N2.
G3 (Bethesda). 2025 Sep 3. doi: 10.1093/g3journal/jkaf205.
Exophiala dermatitidis is a polyextremotolerant black yeast species. E. dermatitidis produces 1,8 dihydroxynaphthalene (DHN) melanin via the Polyketide Synthase 1 (PKS1) pathway enabling it to survive harmful conditions. This study focused on random nontargeted mutagenesis to obtain albino (alb) and hyper-pigmented (hyp) mutants. Notably, all 17 alb mutants possessed mutations in PKS1 whereas the 113 hyper-pigmented (hyp) mutants harbored mutations impacting a range of functions. Cell morphology and phenotypic assays showed additional differences between the alb and hyp mutants. Strikingly, three of the albino mutants (alb1, alb2, and alb3) were conditional in that despite the presence of mutations in PKS1 they were able to produce melanin upon exposure to different carbon sources. These mutants otherwise shared similar cell morphology and growth patterns with the obligate albinos. No additional shared mutations were found among the conditional albinos. Temperature and UV irradiation assays demonstrated reduced growth of albino mutants at higher temperatures (i.e., 42°C) and a greater sensitivity to higher doses of UV. Single nucleotide variant (SNVs) calling showed that some hyperpigmented mutants had a greater number of SNVs compared to albino strains. To date this is the first study to generate and characterize conditional albino mutants in E. dermatitidis with the ability to recover melanin production.
皮炎外瓶霉是一种多极端耐受的黑色酵母菌种。皮炎外瓶霉通过聚酮合酶1（PKS1）途径产生1,8 - 二羟基萘（DHN）黑色素，使其能够在有害条件下存活。本研究聚焦于随机非靶向诱变以获得白化（alb）和色素沉着过度（hyp）突变体。值得注意的是，所有17个alb突变体在PKS1中都存在突变，而113个色素沉着过度（hyp）突变体则含有影响一系列功能的突变。细胞形态学和表型分析显示alb和hyp突变体之间存在其他差异。引人注目的是，三个白化突变体（alb1、alb2和alb3）具有条件性，即尽管PKS1中存在突变，但它们在暴露于不同碳源时仍能够产生黑色素。这些突变体在其他方面与纯合白化体具有相似的细胞形态和生长模式。在条件性白化体中未发现其他共同突变。温度和紫外线照射试验表明，白化突变体在较高温度（即42°C）下生长减缓，对较高剂量的紫外线更敏感。单核苷酸变异（SNV）分析表明，与白化菌株相比，一些色素沉着过度的突变体具有更多的SNV。迄今为止，这是第一项在皮炎外瓶霉中生成并表征具有恢复黑色素产生能力的条件性白化突变体的研究。
