Departament of Biochemistry and Molecular Biology, Federal University of Ceará, Fortaleza, Ceará, Brazil.
PLoS One. 2013 Jul 22;8(7):e70425. doi: 10.1371/journal.pone.0070425. Print 2013.
Soybean toxin (SBTX) is an antifungal protein from soybeans with broad inhibitory activity against the growth and filamentation of many fungi, including human and plant pathogenic species such as Candida albicans, Candida parapsilosis, Aspergillus niger, Penicillium herquei, Cercospora sojina and Cercospora kikuchii. Understanding the mechanism by which SBTX acts on fungi and yeasts may contribute to the design of novel antifungal drugs and/or the development of transgenic plants resistant to pathogens. To this end, the polymorphic yeast C. albicans was chosen as a model organism and changes in the gene expression profile of strain SC5314 upon exposure to SBTX were examined. Genes that were differentially regulated in the presence of SBTX were involved in glucose transport and starvation-associated stress responses as well as in the control of both the induction and repression of C. albicans hyphal formation. Transmission electron microscopy showed that C. albicans cells exposed to SBTX displayed severe signs of starvation and were heavily granulated. Our data were indicative of C. albicans cell starvation despite sufficient nutrient availability in the medium; therefore, it can be speculated that SBTX blocks nutrient uptake systems. Because neither the starvation signal nor the alkaline response pathway lead to the induction of hyphae, we hypothesise that conflicting signals are transmitted to the complex regulatory network controlling morphogenesis, eventually preventing the filamentation signal from reaching a significant threshold.
大豆毒素（SBTX）是一种来自大豆的抗真菌蛋白，对许多真菌的生长和丝状生长具有广泛的抑制活性，包括白色念珠菌、近平滑念珠菌、黑曲霉、青霉赫奎变种、大豆生链格孢和柯氏长蠕孢等人类和植物病原物种。了解 SBTX 对真菌和酵母的作用机制可能有助于设计新型抗真菌药物和/或开发对病原体具有抗性的转基因植物。为此，选择多态性酵母白色念珠菌作为模型生物，研究了 SBTX 暴露后 SC5314 菌株的基因表达谱变化。在 SBTX 存在下差异调节的基因参与葡萄糖转运和与饥饿相关的应激反应，以及控制白色念珠菌菌丝形成的诱导和抑制的控制。透射电子显微镜显示，暴露于 SBTX 的白色念珠菌细胞显示出严重的饥饿迹象，并严重颗粒化。尽管培养基中存在足够的营养物质，但我们的数据表明白色念珠菌细胞处于饥饿状态；因此，可以推测 SBTX 阻断了营养摄取系统。由于饥饿信号和碱性反应途径都不会导致菌丝的诱导，我们假设相互冲突的信号被传递到控制形态发生的复杂调控网络，最终阻止了丝状形成信号达到显著阈值。
