Genomic data have identified a class of fungal specific transcription factors (FsTFs) that are thought to regulate unique aspects of fungal gene expression, although the functions of many of these proteins remain unknown. Here, a novel FsTF (BbStf1), which features a leucine zipper dimerization domain and a fungal transcription factor regulatory middle homology region, was characterized in Beauveria bassiana, a filamentous insect fungal pathogen. Transcriptional activation and nuclear localization were experimentally confirmed for BbStf1. Disruption of Bbstf1 resulted in increased tolerance to oxidative stress and cell wall perturbation, accompanied by increased peroxidase (POD) and superoxide dismutase (SOD) activities and ratio of reduced/oxidized glutathione (GSH/GSSG), and by thickened cell wall and altered composition. Gene expression profile analysis revealed that transcription patterns of antioxidant enzyme and cell wall integrity-involved genes were altered in the ∆Bbstf1, including some BbStf1-targeted genes clarified with evidence. The ∆Bbstf1 strain displayed greater virulence to Galleria mellonella in the bioassays through both topical infection and intrahaemocoel injection due to more rapid proliferation in the haemocoel as compared to the wild-type strain. Altogether, BbStf1 acts as a negative regulator of antioxidant response, cell wall integrity and virulence in B. bassiana.

中文翻译：

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一种新的转录因子负调节真菌昆虫病原体白僵菌的抗氧化反应、细胞壁完整性和毒力

基因组数据已经确定了一类真菌特异性转录因子 (FsTF)，它们被认为可以调节真菌基因表达的独特方面，尽管其中许多蛋白质的功能仍然未知。在这里，一种新型 FsTF (BbStf1) 具有亮氨酸拉链二聚化结构域和真菌转录因子调节中间同源区，在白僵菌（一种丝状昆虫真菌病原体）中得到了表征。实验证实了 BbStf1 的转录激活和核定位。Bbstf1的中断导致对氧化应激和细胞壁扰动的耐受性增加，伴随着过氧化物酶 (POD) 和超氧化物歧化酶 (SOD) 活性和还原/氧化谷胱甘肽 (GSH/GSSG) 的比例增加，以及细胞壁增厚和组成改变。基因表达谱分析显示抗氧化酶和细胞壁完整性相关基因的转录模式在 ∆ Bbstf1中发生了改变，包括一些有证据表明的 BbStf1 靶向基因。Δ Bbstf1菌株对大花菌表现出更强的毒力在通过局部感染和血腔内注射的生物测定中，由于与野生型菌株相比，血腔中的增殖更快。总之，BbStf1 在B. bassiana中充当抗氧化反应、细胞壁完整性和毒力的负调节剂。