The transcription factor Ndt80 is a repressor of <i>Candida parapsilosis</i> virulence attributes

<i>Candida parapsilosis</i> is an emergent opportunistic yeast among hospital settings that affects mainly neonates and immunocompromised patients. Its most remarkable virulence traits are the ability to adhere to prosthetic materials, as well as the formation of biofilm on abiotic surfaces. The Ndt80 transcription factor was identified as one of the regulators of biofilm formation by <i>C. parapsilosis</i>; however, its function in this process was not yet clarified. By knocking out <i>NDT80</i> (<i>CPAR2-213640</i>) gene, or even just one single copy of the gene, we observed substantial alterations of virulence attributes, including morphogenetic changes, adhesion and biofilm growth profiles. Both <i>ndt80Δ</i> and <i>ndt80ΔΔ</i> mutants changed colony and cell morphologies from smooth, yeast-shaped to crepe and pseudohyphal elongated forms, exhibiting promoted adherence to polystyrene microspheres and notably, forming a higher amount of biofilm compared to wild-type strain. Interestingly, we identified transcription factors Ume6, Cph2, Cwh41, Ace2, Bcr1, protein kinase Mkc1 and adhesin Als7 to be under Ndt80 negative regulation, partially explaining the phenotypes displayed by the <i>ndt80ΔΔ</i> mutant. Furthermore, <i>ndt80ΔΔ</i> pseudohyphae adhered more rapidly and were more resistant to murine macrophage attack, becoming deleterious to such cells after phagocytosis. Unexpectedly, our findings provide the first evidence for a direct role of Ndt80 as a repressor of <i>C. parapsilosis</i> virulence attributes. This finding shows that <i>C. parapsilosis</i> Ndt80 functionally diverges from its homolog in the close related fungal pathogen <i>C. albicans</i>.

近平滑假丝酵母（*Candida parapsilosis*）是医院环境中新兴的机会致病性酵母菌，主要感染新生儿与免疫功能低下患者。其最显著的毒力性状包括黏附医用假体材料的能力，以及在非生物表面形成生物被膜的能力。Ndt80转录因子（Ndt80 transcription factor）已被鉴定为近平滑假丝酵母生物被膜形成的调控因子之一，但其在该过程中的具体功能尚未阐明。本研究通过敲除*NDT80*（*CPAR2-213640*）基因，甚至仅敲除该基因的单拷贝，均观察到菌株毒力相关表型发生显著改变，包括形态发生变化、黏附能力与生物被膜生长特性的改变。*ndt80Δ*与*ndt80ΔΔ*突变株的菌落及细胞形态均从光滑的酵母型转变为皱缩假菌丝伸长型，相较于野生型菌株，其对聚苯乙烯微球的黏附能力增强，且可形成更多的生物被膜。值得注意的是，本研究鉴定出转录因子Ume6、Cph2、Cwh41、Ace2、Bcr1，蛋白激酶Mkc1以及黏附素Als7均受Ndt80的负调控，这部分解释了*ndt80ΔΔ*突变株所呈现的表型。此外，*ndt80ΔΔ*突变株的假菌丝黏附速度更快，且对小鼠巨噬细胞的吞噬杀伤抵抗力更强，在被巨噬细胞吞噬后可对宿主细胞产生杀伤作用。出乎意料的是，本研究结果首次证明Ndt80可作为近平滑假丝酵母毒力性状的负调控因子发挥直接作用。这一结果表明，近平滑假丝酵母的Ndt80功能与亲缘关系相近的病原菌白色念珠菌（*Candida albicans*）中的同源蛋白存在功能分化。