Human fungal pathogen Candida albicans cannot utilize L‐sorbose as a sole carbon source. However, chromosome 5 monosomic strains can grow on sorbose as repressors present on this chromosome get diminished allowing the expression of sorbose utilization gene (SOU1) located on chromosome 4. Functional identification of these repressors has been a difficult task as they are scattered on a large portion of the right arm of chromosome 5. Herein, we have applied the telomere‐mediated chromosomal truncation approach to identify a novel repressor for sorbose utilization in this pathogen. Multiple systematic chromosomal truncations were performed on the right arm of Chr5 in the background of csu51∆/CSU51 to minimize the functional region to 6‐kb chromosomal stretch. Further, truncation that removes the part of Orf19.3942 strongly suggested its role in sorbose utilization. However, compelling evidence comes from the observation that truncation at 1,044.288‐kb position of Chr5 in the strain csu51∆/CSU51 orf19.3942∆/Orf.19.3942 produced Sou⁺ phenotype; otherwise, the strain remains Sou⁻. This confirms beyond doubt the role of Orf.19.3942 in the regulation of sorbose utilization and designated as CSU57. Comparison of SOU1 gene expression of Sou⁺ strains with wild type suggested its role at transcriptional level. Strain carrying double disruption of CSU57 remains Sou⁻. Co‐overexpression of SOU1 and CSU57 together does not make the recipient strain Sou⁻; however, multiple tandem copies of CSU57 produced diminished growth compared with control suggesting that it is a weak repressor. Taken together, we report that CSU57 encodes a novel repressor of L‐sorbose utilization in this pathogen.

中文翻译：

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CSU57 在机会性人类真菌病原体白色念珠菌中编码一种新型山梨糖利用阻遏物

人类真菌病原体白色念珠菌不能利用 L-山梨糖作为唯一的碳源。然而，5 号染色体单体菌株可以在山梨糖上生长，因为该染色体上存在的阻遏物减少，从而允许位于 4 号染色体上的山梨糖利用基因 ( SOU1 )表达。这些阻遏物的功能鉴定一直是一项艰巨的任务，因为它们分散在一个大的区域。 5号染色体右臂的一部分。在此，我们应用端粒介导的染色体截断方法来鉴定该病原体中山梨糖利用的新型阻遏物。在csu51 ∆/ CSU51的背景下，在Chr5 的右臂上进行了多次系统染色体截断将功能区最小化为 6-kb 染色体伸展。此外，去除Orf19.3942部分的截断强烈表明其在山梨糖利用中的作用。然而，令人信服的证据来自观察到在菌株csu51 Δ/ CSU51 orf19.3942 Δ/ Orf.19.3942中 Chr5 的 1,044.288-kb 位置截断产生 Sou ⁺表型；否则，应变仍然是 Sou ^-。这无疑证实了Orf.19.3942在调节山梨糖利用并被指定为CSU57 中的作用。Sou ⁺的SOU1基因表达比较野生型菌株表明其在转录水平上的作用。携带CSU57双重破坏的菌株仍然是 Sou ^-。SOU1和CSU57 的共同过表达不会使受体菌株 Sou ^-；然而，与对照相比，CSU57 的多个串联拷贝产生的生长减弱，表明它是一种弱阻遏物。总之，我们报告说CSU57在该病原体中编码了一种新型的 L-山梨糖利用阻遏物。